Recent Publications

Infect Genet Evol. 2023 May 26:105446. doi: 10.1016/j.meegid.2023.105446. Online ahead of print.

ABSTRACT

Studies on antimicrobial resistance (AMR) profiles and epidemiological affirmation for AMR transmission are limited in fisheries and aquaculture settings. Since 2015, based on Global Action Plan on AMR by World Health Organization (WHO) and World Organization for Animal Health (OIE), several initiatives have been under taken to enhance the knowledge, skills and capacity to establish AMR trends through surveillance and strengthening of epidemiological evidence. The focus of this study was to determine the prevalence of antimicrobial resistance (AMR), its resistance profiles and molecular characterization with respect to phylogroups, antimicrobial resistance genes (ARGs), virulence genes (VGs), quaternary ammonium compounds resistance (QAC) genes and plasmid typing in retail market fishes. Pulse field gel electrophoresis (PFGE) to understand the genetic lineage of the two most important Enterobacteriaceae members, E. coli and Klebsiella sp. was performed. 94 fish samples were collected from three different sites viz., Silagrant (S1), Garchuk (S2) and North Guwahati Town Committee (NGTC) Region (S3) in Guwahati, Assam. Out of the 113 microbial isolates from the fish samples, 45 (39.82%) were E. coli; 23 (20.35%) belonged to Klebsiella genus. Among E. coli, 48.88% (n = 22) of the isolates were alerted by the BD Phoenix M50 instrument as ESBL, 15.55% (n = 7) as PCP and 35.55% (n = 16) as non-ESBL. E. coli (39.82%) was the most prevalent pathogen among the Enterobacteriaceae members screened and showed resistance to ampicillin (69%) followed by cefazoline (64%), cefotaxime (49%) and piperacillin (49%). In the present study, 66.66% of E. coli and 30.43% of Klebsiella sp. were categorized as multi drug resistance (MDR) bacteria. CTX-M-gp-1, with CTX-M-15 variant (47%), was the most widely circulating beta-lactamase gene, while other ESBL genes blaTEM (7%), blaSHV (2%) and blaOXA-1-like (2%) were also identified in E. coli. Out of the 23 isolates of Klebsiella, 14(60.86%) were ampicillin (AM)-resistant (11(47.82%) K. oxytoca, 3(13.04%) K. aerogenes), whereas 8(34.78%) isolates of K. oxytoca showed intermediate resistance to AM. All Klebsiella isolates were susceptible to AN, SCP, MEM and TZP, although two K. aerogenes were resistant to imipenem. DHA and LAT genes were detected, respectively, in 7(16%) and 1(2%) of the E. coli strains while a single K. oxytoca (4.34%) isolate carried MOX, DHA and blaCMY-2 genes. The fluoroquinolone resistance genes identified in E. coli included qnrB (71%), qnrS (84%), oqxB (73%) and aac(6)-Ib-cr (27%); however, in Klebsiella, these genes, respectively, had a prevalence of 87%, 26%, 74% and 9%. The E. coli isolates belonged to phylogroup A(47%), B1(33%) and D(14%). All of the 22(100%) ESBL E. coli had chromosome-mediated disinfectant resistance genes viz., ydgE, ydgF, sugE(c), mdfA while 82% of ESBL E. coli had emrE. Among the non-ESBL E. coli isolates, 87% of them showed the presence of ydgE, ydgF and sugE(c) genes, while 78% of the isolates had mdfA and 39% had emrE genes respectively. 59% of the ESBL and 26% of the non-ESBL E. coli had showed the presence of qacEΔ1. The sugE(p) was present in 27% of the ESBL-producing E. coli and in 9% of non-ESBL isolates. Out of the 3 ESBL-producing Klebsiella isolates, 2(66.66%) K. oxytoca isolates were found harboring plasmid-mediated qacEΔ1 gene while one (33.33%) K. oxytoca isolate had sugE(p) gene. IncFI was the most prevalent plasmid type detected in the isolates studied, with A/C (18%), P (14%), X, Y (9% each) and I1-Iγ (14%, 4%). 50% (n = 11) of the ESBL and 17% (n = 4) of the non-ESBL E. coli isolates harboured IncFIB and 45% (n = 10) ESBL and one (4.34%) non-ESBL E. coli isolates harboured IncFIA. Dominance of E. coli over other Enterobacterales and diverse phylogenetic profiles of E. coli and Klebsiella sp. suggests the possibility of contamination and this may be due to compromised hygienic practices along the supply chain and contamination of aquatic ecosystem. Continuous surveillance in domestic markets must be a priority in addressing antimicrobial resistance in fishery settings and to identify any unwarranted epidemic clones of E. coli and Klebsiella that can challenge public health sector.

PMID:37245778 | DOI:10.1016/j.meegid.2023.105446

Sci Rep. 2023 May 25;13(1):8518. doi: 10.1038/s41598-023-35726-z.

ABSTRACT

Wolbachia is a common endosymbiont that can protect insects against viral pathogens. However, whether the antiviral effects of Wolbachia have a significant effect on fitness remains unclear. We have investigated the interaction between Drosophila melanogaster, Wolbachia and two viruses that we recently isolated from wild flies, La Jolla virus (LJV; Iflaviridae) and Newfield virus (NFV; Permutotetraviridae). Flies infected with these viruses have increased mortality rates, and NFV partially sterilizes females. These effects on fitness were reduced in Wolbachia-infected flies, and this was associated with reduced viral titres. However, Wolbachia alone also reduces survival, and under our experimental conditions these costs of the symbiont can outweigh the benefits of antiviral protection. In contrast, protection against the sterilizing effect of NFV leads to a net benefit of Wolbachia infection after exposure to the virus. These results support the hypothesis that Wolbachia is an important defense against the natural pathogens of D. melanogaster. Furthermore, by reducing the cost of Wolbachia infection, the antiviral effects of Wolbachia may aid its invasion into populations and help explain why it is so common in nature.

PMID:37231093 | DOI:10.1038/s41598-023-35726-z

PLoS Pathog. 2023 May 25;19(5):e1011037. doi: 10.1371/journal.ppat.1011037. eCollection 2023 May.

ABSTRACT

Schistosoma haematobium is the most prevalent of the human-infecting schistosome species, causing significant morbidity in endemically exposed populations. Despite this, it has been relatively understudied compared to its fellow species, S. mansoni. Here we provide the first comprehensive characterization of the S. haematobium Tegument Allergen-Like protein family, a key protein family directly linked to protective immunity in S. mansoni infection. Comparable with observations for S. mansoni, parasite phylogenetic analysis and relative gene expression combined with host serological analysis support a cross-reactive relationship between S. haematobium TAL proteins, exposed to the host immune system as adult worms die, and closely related proteins, exposed during penetration by the infecting cercarial and early schistosomulae stages. Specifically, our results strengthen the evidence for host immunity driven by cross-reactivity between family members TAL3 and TAL5, establishing it for the first time for S. haematobium infection. Furthermore, we build upon this relationship to include the involvement of an additional member of the TAL protein family, TAL11 for both schistosome species. Finally, we show a close association between experience of infection and intensity of transmission and the development of protective IgE responses to these antigens, thus improving our knowledge of the mechanisms by which protective host immune responses develop. This knowledge will be critical in understanding how control efforts such as mass drug administration campaigns influence the development of host immunity and subsequent patterns of infection and disease within endemic populations.

PMID:37228019 | DOI:10.1371/journal.ppat.1011037

Microb Genom. 2023 May;9(5). doi: 10.1099/mgen.0.001021.

ABSTRACT

Horizontal gene transfer (HGT) and the resulting patterns of gene gain and loss are a fundamental part of bacterial evolution. Investigating these patterns can help us to understand the role of selection in the evolution of bacterial pangenomes and how bacteria adapt to a new niche. Predicting the presence or absence of genes can be a highly error-prone process that can confound efforts to understand the dynamics of horizontal gene transfer. This review discusses both the challenges in accurately constructing a pangenome and the potential consequences errors can have on downstream analyses. We hope that by summarizing these issues researchers will be able to avoid potential pitfalls, leading to improved bacterial pangenome analyses.

PMID:37227251 | DOI:10.1099/mgen.0.001021

Microlife. 2020 Oct 17;1(1):uqaa002. doi: 10.1093/femsml/uqaa002. eCollection 2020.

ABSTRACT

Small proteins are an emerging class of gene products with diverse roles in bacterial physiology. However, a full understanding of their importance has been hampered by insufficient genome annotations and a lack of comprehensive characterization in microbes other than Escherichia coli. We have taken an integrative approach to accelerate the discovery of small proteins and their putative virulence-associated functions in Salmonella Typhimurium. We merged the annotated small proteome of Salmonella with new small proteins predicted with in silico and experimental approaches. We then exploited existing and newly generated global datasets that provide information on small open reading frame expression during infection of epithelial cells (dual RNA-seq), contribution to bacterial fitness inside macrophages (Transposon-directed insertion sequencing), and potential engagement in molecular interactions (Grad-seq). This integrative approach suggested a new role for the small protein MgrB beyond its known function in regulating PhoQ. We demonstrate a virulence and motility defect of a Salmonella ΔmgrB mutant and reveal an effect of MgrB in regulating the Salmonella transcriptome and proteome under infection-relevant conditions. Our study highlights the power of interpreting available 'omics' datasets with a focus on small proteins, and may serve as a blueprint for a data integration-based survey of small proteins in diverse bacteria.

PMID:37223003 | PMC:PMC10117436 | DOI:10.1093/femsml/uqaa002

Front Microbiol. 2023 May 4;14:1128966. doi: 10.3389/fmicb.2023.1128966. eCollection 2023.

ABSTRACT

Brucellosis remains one of the most significant zoonotic diseases globally, responsible for both considerable human morbidity and economic losses due to its impacts on livestock productivity. Despite this, there remain significant evidence gaps in many low- and middle-income countries, including those of sub-Saharan Africa. Here we report the first molecular characterisation of Brucella sp. from Ethiopia. Fifteen Brucella sp. isolates from an outbreak in cattle from a herd in central Ethiopia were identified as Brucella abortus, using bacterial culture and molecular methods. Sequencing of the Ethiopian B. abortus isolates allowed their phylogenetic comparison with 411 B. abortus strains of diverse geographical origins, using whole genome single nucleotide polymorphisms (wgSNP). The Ethiopian isolates belonged to an early-branching lineage (Lineage A) previously only represented by data from two strains, both of sub-Saharan African origin (Kenya and Mozambique). A second B. abortus lineage (Lineage B), also comprised solely of strains originating from sub-Saharan Africa, was identified. The majority of strains belonged to one of two lineages of strains originating from a much broader geographical range. Further analyses based on multi-locus sequence typing (MLST) and multi-locus variable-number tandem repeat analysis (MLVA) expanded the number of B. abortus strains available for comparison with the Ethiopian isolates and were consistent with the findings from wgSNP analysis. MLST profiles of the Ethiopian isolates expanded the sequence type (ST) diversity of the early branching lineage of B. abortus, equivalent to wgSNP Lineage A. A more diverse cluster of STs, equivalent to wgSNP Lineage B, was comprised solely of strains originating from sub-Saharan Africa. Similarly, analysis of B. abortus MLVA profiles (n = 1891) confirmed that the Ethiopian isolates formed a unique cluster, similar to only two existing strains, and distinct from the majority of other strains of sub-Saharan African origin. These findings expand the known diversity of an under-represented lineage of B. abortus and suggest a potential evolutionary origin for the species in East Africa. In addition to providing information concerning Brucella species extant within Ethiopia this work serves as the basis for further studies on the global population structure and evolutionary history of a major zoonotic pathogen.

PMID:37213520 | PMC:PMC10192883 | DOI:10.3389/fmicb.2023.1128966

Nat Methods. 2023 May 19. doi: 10.1038/s41592-023-01904-0. Online ahead of print.

NO ABSTRACT

PMID:37208420 | DOI:10.1038/s41592-023-01904-0

Org Biomol Chem. 2023 May 19. doi: 10.1039/d3ob00351e. Online ahead of print.

ABSTRACT

Fragment-based lead discovery (FBLD) often relies on flat, aromatic compounds which display undesirable physicochemical properties with limited exit vectors for fragment growth. Herein, we report concise synthetic strategies to sp3-rich heterocyclic fragments encompassing polar exit vectors poised for fragment-to-lead (F2L) development.

PMID:37203457 | DOI:10.1039/d3ob00351e

Microb Genom. 2023 May;9(5). doi: 10.1099/mgen.0.000976.

ABSTRACT

The National Collection of Type Cultures (NCTC) was founded on 1 January 1920 in order to fulfil a recognized need for a centralized repository for bacterial and fungal strains within the UK. It is among the longest-established collections of its kind anywhere in the world and today holds approximately 6000 type and reference bacterial strains - many of medical, scientific and veterinary importance - available to academic, health, food and veterinary institutions worldwide. Recently, a collaboration between NCTC, Pacific Biosciences and the Wellcome Sanger Institute established the NCTC3000 project to long-read sequence and assemble the genomes of up to 3000 NCTC strains. Here, at the beginning of the collection's second century, we introduce the resulting NCTC3000 sequence read datasets, genome assemblies and annotations as a unique, historically and scientifically relevant resource for the benefit of the international bacterial research community.

PMID:37194944 | DOI:10.1099/mgen.0.000976

BMC Public Health. 2023 May 16;23(1):899. doi: 10.1186/s12889-023-15824-3.

ABSTRACT

Livestock value chains constitute a source of livelihood for meat and milk value chain actors in Ethiopia, from dairy farmers to other associated value chain actors such as milk traders, abattoir workers, public health officials, veterinarians, butcheries selling meats, milk cooperatives, artisanal milk processors, and transporters. The development of these livestock value chains, however, is constrained by poor food safety and quality, while consumers are also exposed to public health risks due to milk and meat value chain actors' food handling and hygiene practices.This study used Photovoice and participant observation to explore meat and milk value chain actors' food handling and hygiene practices in suburban areas of Addis Ababa and neighbouring Oromia in Ethiopia. The results of this study reveal that milk and meat value chain actors' food handling practices are not aligned with the recommended Ethiopian food safety and quality standards. Low compliance with food safety and quality standards reflected a combination of factors such as lack of incentives, poor road infrastructure and low enforcement of food safety standards.Participatory and visual research methods enable a researcher to collect context-aware data that can lead to the development of policies and intervention strategies that reflect local needs and priorities. The results of this study affirm the need to identify socially acceptable and economically viable policies and intervention strategies that are acceptable to all chain actors; and suggest there is an imperative to train milk and meat value chain actors on good hygiene handling practices, improve road infrastructure, and facilitate access equipment such as fridges and freezers that can contribute to maintaining food safety and quality.

PMID:37193991 | DOI:10.1186/s12889-023-15824-3

Microb Genom. 2023 May;9(5). doi: 10.1099/mgen.0.001018.

ABSTRACT

Exposure to different mutagens leaves distinct mutational patterns that can allow inference of pathogen replication niches. We therefore investigated whether SARS-CoV-2 mutational spectra might show lineage-specific differences, dependent on the dominant site(s) of replication and onwards transmission, and could therefore rapidly infer virulence of emergent variants of concern (VOCs). Through mutational spectrum analysis, we found a significant reduction in G>T mutations in the Omicron variant, which replicates in the upper respiratory tract (URT), compared to other lineages, which replicate in both the URT and lower respiratory tract (LRT). Mutational analysis of other viruses and bacteria indicates a robust, generalizable association of high G>T mutations with replication within the LRT. Monitoring G>T mutation rates over time, we found early separation of Omicron from Beta, Gamma and Delta, while mutational patterns in Alpha varied consistent with changes in transmission source as social restrictions were lifted. Mutational spectra may be a powerful tool to infer niches of established and emergent pathogens.

PMID:37185044 | DOI:10.1099/mgen.0.001018

Synth Biol (Oxf). 2023 Apr 20;8(1):ysad009. doi: 10.1093/synbio/ysad009. eCollection 2023.

ABSTRACT

While synthetic biology is hoped to hold promise and potential to address pressing global challenges, the issue of regulation is an under-appreciated challenge. Particularly in Europe, the regulatory frameworks involved are rooted in historical concepts based on containment and release. Through a series of case studies including a field-use biosensor intended to detect arsenic in well water in Nepal and Bangladesh, and insects engineered for sterility, we explore the implications that this regulatory and conceptual divide has had on the deployment of synthetic biology projects in different national contexts. We then consider some of the broader impacts that regulation can have on the development of synthetic biology as a field, not only in Europe but also globally, with a particular emphasis on low- and middle-income countries. We propose that future regulatory adaptability would be increased by moving away from a containment and release dichotomy and toward a more comprehensive assessment that accounts for the possibility of varying degrees of 'contained release'. Graphical Abstract.

PMID:37180978 | PMC:PMC10173542 | DOI:10.1093/synbio/ysad009

Biochem Biophys Res Commun. 2023 May 2;666:61-67. doi: 10.1016/j.bbrc.2023.04.088. Online ahead of print.

ABSTRACT

The RGD motif on the SARS-CoV-2 spike protein has been suggested to interact with RGD-binding integrins αVβ3 and α5β1 to enhance viral cell entry and alter downstream signaling cascades. The D405N mutation on the Omicron subvariant spike proteins, resulting in an RGN motif, has recently been shown to inhibit binding to integrin αVβ3. Deamidation of asparagines in protein ligand RGN motifs has been demonstrated to generate RGD and RGisoD motifs that permit binding to RGD-binding integrins. Two asparagines, N481 and N501, on the Wild-type spike receptor-binding domain have been previously shown to have deamidation half-lives of 16.5 and 123 days, respectively, which may occur during the viral life cycle. Deamidation of Omicron subvariant N405 may recover the ability to interact with RGD-binding integrins. Thus, herein, all-atom molecular dynamics simulations of the Wild-type and Omicron subvariant spike protein receptor-binding domains were conducted to investigate the potential for asparagines, the Omicron subvariant N405 in particular, to assume the optimized geometry for deamidation to occur. In summary, the Omicron subvariant N405 was primarily found to be stabilized in a state unfavourable for deamidation after hydrogen bonding with downstream E406. Nevertheless, a small number of RGD or RGisoD motifs on the Omicron subvariant spike proteins may restore the ability to interact with RGD-binding integrins. The simulations also provided structural clarification regarding the deamidation rates of Wild-type N481 and N501 and highlighted the utility of tertiary structure dynamics information in predicting asparagine deamidation. Further work is needed to characterize the effects of deamidation on spike-integrin interactions.

PMID:37178506 | DOI:10.1016/j.bbrc.2023.04.088

PLoS Pathog. 2023 May 12;19(5):e1010992. doi: 10.1371/journal.ppat.1010992. Online ahead of print.

ABSTRACT

The genomes of both human cytomegalovirus (HCMV) and murine cytomegalovirus (MCMV) were first sequenced over 20 years ago. Similar to HCMV, the MCMV genome had initially been proposed to harbor ≈170 open reading frames (ORFs). More recently, omics approaches revealed HCMV gene expression to be substantially more complex comprising several hundred viral ORFs. Here, we provide a state-of-the art reannotation of lytic MCMV gene expression based on integrative analysis of a large set of omics data. Our data reveal 365 viral transcription start sites (TiSS) that give rise to 380 and 454 viral transcripts and ORFs, respectively. The latter include >200 small ORFs, some of which represented the most highly expressed viral gene products. By combining TiSS profiling with metabolic RNA labelling and chemical nucleotide conversion sequencing (dSLAM-seq), we provide a detailed picture of the expression kinetics of viral transcription. This not only resulted in the identification of a novel MCMV immediate early transcript encoding the m166.5 ORF, which we termed ie4, but also revealed a group of well-expressed viral transcripts that are induced later than canonical true late genes and contain an initiator element (Inr) but no TATA- or TATT-box in their core promoters. We show that viral upstream ORFs (uORFs) tune gene expression of longer viral ORFs expressed in cis at translational level. Finally, we identify a truncated isoform of the viral NK-cell immune evasin m145 arising from a viral TiSS downstream of the canonical m145 mRNA. Despite being ≈5-fold more abundantly expressed than the canonical m145 protein it was not required for downregulating the NK cell ligand, MULT-I. In summary, our work will pave the way for future mechanistic studies on previously unknown cytomegalovirus gene products in an important virus animal model.

PMID:37172056 | DOI:10.1371/journal.ppat.1010992

J Am Chem Soc. 2023 May 10. doi: 10.1021/jacs.3c01493. Online ahead of print.

ABSTRACT

Cells can precisely program the shape and lateral organization of their membranes using protein machinery. Aiming to replicate a comparable degree of control, here we introduce DNA-origami line-actants (DOLAs) as synthetic analogues of membrane-sculpting proteins. DOLAs are designed to selectively accumulate at the line-interface between coexisting domains in phase-separated lipid membranes, modulating the tendency of the domains to coalesce. With experiments and coarse-grained simulations, we demonstrate that DOLAs can reversibly stabilize two-dimensional analogues of Pickering emulsions on synthetic giant liposomes, enabling dynamic programming of membrane lateral organization. The control afforded over membrane structure by DOLAs extends to three-dimensional morphology, as exemplified by a proof-of-concept synthetic pathway leading to vesicle fission. With DOLAs we lay the foundations for mimicking, in synthetic systems, some of the critical membrane-hosted functionalities of biological cells, including signaling, trafficking, sensing, and division.

PMID:37163977 | DOI:10.1021/jacs.3c01493

Nucleic Acids Res. 2023 May 9:gkad341. doi: 10.1093/nar/gkad341. Online ahead of print.

ABSTRACT

Coordination of bacterial stress response mechanisms is critical for long-term survival in harsh environments for successful host infection. The general and specific stress responses of well-studied Gram-negative pathogens like Escherichia coli are controlled by alternative sigma factors, archetypically RpoS. The deadly hospital pathogen Acinetobacter baumannii is notoriously resistant to environmental stresses, yet it lacks RpoS, and the molecular mechanisms driving this incredible stress tolerance remain poorly defined. Here, using functional genomics, we identified the transcriptional regulator DksA as a master regulator for broad stress protection and virulence in A. baumannii. Transcriptomics, phenomics and in vivo animal studies revealed that DksA controls ribosomal protein expression, metabolism, mutation rates, desiccation, antibiotic resistance, and host colonization in a niche-specific manner. Phylogenetically, DksA was highly conserved and well-distributed across Gammaproteobacteria, with 96.6% containing DksA, spanning 88 families. This study lays the groundwork for understanding DksA as a major regulator of general stress response and virulence in this important pathogen.

PMID:37158230 | DOI:10.1093/nar/gkad341

Adv Mater. 2023 May 8:e2301562. doi: 10.1002/adma.202301562. Online ahead of print.

ABSTRACT

State-of-the-art bottom-up synthetic biology allows us to replicate many basic biological functions in artificial cell-like devices. To mimic more complex behaviours, however, artificial cells would need to perform many of these functions in a synergistic and coordinated fashion, which remains elusive. Here we considered a sophisticated biological response, namely the capture and deactivation of pathogens by neutrophil immune cells, through the process of netosis. We designed a consortium consisting of two synthetic agents - responsive DNA-based particles and antibiotic-loaded lipid vesicles - whose coordinated action mimics the sought immune-like response when triggered by bacterial metabolism. The artificial netosis-like response emerges from a series of interlinked sensing and communication pathways between the live and synthetic agents, and translates into both physical and chemical antimicrobial actions, namely bacteria immobilisation and exposure to antibiotics. Our results demonstrate how advanced life-like responses can be prescribed with a relatively small number of synthetic molecular components, and outlines a new strategy for artificial-cell-based antimicrobial solutions. This article is protected by copyright. All rights reserved.

PMID:37156014 | DOI:10.1002/adma.202301562

Am J Hypertens. 2023 May 6:hpad045. doi: 10.1093/ajh/hpad045. Online ahead of print.

ABSTRACT

Cytomegalovirus (CMV) is a member of the β- herpesviruses and is ubiquitous, infecting 50-99% of the human population depending on ethnic and socioeconomic conditions. CMV establishes lifelong, latent infections in their host. Spontaneous reactivation of CMV is usually asymptomatic, but reactivation events in immunocompromised or immunosuppressed individuals can lead to severe morbidity and mortality. Moreover, herpesvirus infections have been associated with several cardiovascular and post-transplant diseases (stroke, atherosclerosis, post-transplant vasculopathy and hypertension). Herpesviruses, including CMV, encode viral G protein-coupled receptors (vGPCRs) that alter the host cell by hijacking signaling pathways that play important roles in the viral life cycle and these cardiovascular diseases. In this brief review, we discuss the pharmacology and signaling properties of these vGPCRs, and their contribution to hypertension. Overall, these vGPCRs can be considered attractive targets moving forward in the development of novel hypertensive therapies.

PMID:37148218 | DOI:10.1093/ajh/hpad045

Contact (Thousand Oaks). 2021 Jan;4:251525642110523. doi: 10.1177/25152564211052382. Epub 2021 Nov 17.

ABSTRACT

Saposins are lipid transfer proteins required for the degradation of sphingolipids in the lysosome. These small proteins bind lipids by transitioning from a closed, monomeric state to an open conformation exposing a hydrophobic surface that binds and shields hydrophobic lipid tails from the aqueous environment. Saposins form a range of multimeric assemblies to encompass these bound lipids and present them to hydrolases in the lysosome. This lipid-binding property of human saposin A has been exploited to form lipoprotein nanodiscs suitable for structural studies of membrane proteins. Here we present the crystal structure of a unique tetrameric assembly of murine saposin A produced serendipitously, following modifications of published protocols for making lipoprotein nanodiscs. The structure of this new saposin oligomer highlights the diversity of tertiary arrangement that can be adopted by these important lipid transfer proteins.

PMID:37143956 | PMC:PMC7614494 | DOI:10.1177/25152564211052382

Science. 2023 May 5;380(6644):466-467. doi: 10.1126/science.adh3426. Epub 2023 May 4.

NO ABSTRACT

PMID:37141376 | DOI:10.1126/science.adh3426