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Gupta S, Roy M, Dey D, Bhakta K, Bhowmick A, Chattopadhyay D, Ghosh A. Archaeal SRP RNA and SRP19 facilitate the assembly of SRP54-FtsY targeting complex. Biochem Biophys Res Commun 2021; 566:53-58. [PMID: 34116357 DOI: 10.1016/j.bbrc.2021.05.087] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/25/2021] [Accepted: 05/26/2021] [Indexed: 10/21/2022]
Abstract
The signal recognition particle (SRP) plays an essential role in protein translocation across biological membranes. Stable complexation of two GTPases in the signal recognition particle (SRP) and its receptor (SR) control the delivery of nascent polypeptide to the membrane translocon. In archaea, protein targeting is mediated by the SRP54/SRP19/7S RNA ribonucleoprotein complex (SRP) and the FtsY protein (SR). In the present study, using fluorescence resonance energy transfer (FRET), we demonstrate that archaeal 7S RNA stabilizes the SRP54·FtsY targeting complex (TC). Moreover, we show that archaeal SRP19 further assists 7S RNA in stabilizing the targeting complex (TC). These results suggest that archaeal 7S RNA and SRP19 modulate the conformation of the targeting complex and thereby reinforce TC to execute protein translocation via concomitant GTP hydrolysis.
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Affiliation(s)
| | - Mousam Roy
- Department of Biochemistry, Bose Institute, Kolkata, India
| | - Dhritiman Dey
- Department of Natural Products, National Institute of Pharmaceutical Education and Research, Kolkata, India
| | - Koustav Bhakta
- Department of Biochemistry, Bose Institute, Kolkata, India
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2
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Gómez-Villegas P, Vigara J, Romero L, Gotor C, Raposo S, Gonçalves B, Léon R. Biochemical Characterization of the Amylase Activity from the New Haloarchaeal Strain Haloarcula sp. HS Isolated in the Odiel Marshlands. BIOLOGY 2021; 10:biology10040337. [PMID: 33923574 PMCID: PMC8073556 DOI: 10.3390/biology10040337] [Citation(s) in RCA: 5] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Received: 02/22/2021] [Revised: 04/14/2021] [Accepted: 04/15/2021] [Indexed: 12/17/2022]
Abstract
Alpha-amylases are a large family of α,1-4-endo-glycosyl hydrolases distributed in all kingdoms of life. The need for poly-extremotolerant amylases encouraged their search in extreme environments, where archaea become ideal candidates to provide new enzymes that are able to work in the harsh conditions demanded in many industrial applications. In this study, a collection of haloarchaea isolated from Odiel saltern ponds in the southwest of Spain was screened for their amylase activity. The strain that exhibited the highest activity was selected and identified as Haloarcula sp. HS. We demonstrated the existence in both, cellular and extracellular extracts of the new strain, of functional α-amylase activities, which showed to be moderately thermotolerant (optimum around 60 °C), extremely halotolerant (optimum over 25% NaCl), and calcium-dependent. The tryptic digestion followed by HPLC-MS/MS analysis of the partially purified cellular and extracellular extracts allowed to identify the sequence of three alpha-amylases, which despite sharing a low sequence identity, exhibited high three-dimensional structure homology, conserving the typical domains and most of the key consensus residues of α-amylases. Moreover, we proved the potential of the extracellular α-amylase from Haloarcula sp. HS to treat bakery wastes under high salinity conditions.
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Affiliation(s)
- Patricia Gómez-Villegas
- Laboratory of Biochemistry, Department of Chemistry, Marine International Campus of Excellence (CEIMAR), University of Huelva, Avda. de las Fuerzas Armadas s/n, 21071 Huelva, Spain; (P.G.-V.); (J.V.)
| | - Javier Vigara
- Laboratory of Biochemistry, Department of Chemistry, Marine International Campus of Excellence (CEIMAR), University of Huelva, Avda. de las Fuerzas Armadas s/n, 21071 Huelva, Spain; (P.G.-V.); (J.V.)
| | - Luis Romero
- Instituto de Bioquímica Vegetal y Fotosíntesis, Consejo Superior de Investigaciones Científicas and Universidad de Sevilla, Avenida Américo Vespucio 49, 41092 Seville, Spain; (L.R.); (C.G.)
| | - Cecilia Gotor
- Instituto de Bioquímica Vegetal y Fotosíntesis, Consejo Superior de Investigaciones Científicas and Universidad de Sevilla, Avenida Américo Vespucio 49, 41092 Seville, Spain; (L.R.); (C.G.)
| | - Sara Raposo
- CIMA—Centre for Marine and Environmental Research, FCT, Campus de Gambelas, Universidade do Algarve, 8005-139 Faro, Portugal; (S.R.); (B.G.)
| | - Brígida Gonçalves
- CIMA—Centre for Marine and Environmental Research, FCT, Campus de Gambelas, Universidade do Algarve, 8005-139 Faro, Portugal; (S.R.); (B.G.)
| | - Rosa Léon
- Laboratory of Biochemistry, Department of Chemistry, Marine International Campus of Excellence (CEIMAR), University of Huelva, Avda. de las Fuerzas Armadas s/n, 21071 Huelva, Spain; (P.G.-V.); (J.V.)
- Correspondence: ; Tel.: +34-959-219-951
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3
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Pohlschroder M, Pfeiffer F, Schulze S, Abdul Halim MF. Archaeal cell surface biogenesis. FEMS Microbiol Rev 2018; 42:694-717. [PMID: 29912330 PMCID: PMC6098224 DOI: 10.1093/femsre/fuy027] [Citation(s) in RCA: 39] [Impact Index Per Article: 6.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/09/2018] [Accepted: 06/12/2018] [Indexed: 12/13/2022] Open
Abstract
Cell surfaces are critical for diverse functions across all domains of life, from cell-cell communication and nutrient uptake to cell stability and surface attachment. While certain aspects of the mechanisms supporting the biosynthesis of the archaeal cell surface are unique, likely due to important differences in cell surface compositions between domains, others are shared with bacteria or eukaryotes or both. Based on recent studies completed on a phylogenetically diverse array of archaea, from a wide variety of habitats, here we discuss advances in the characterization of mechanisms underpinning archaeal cell surface biogenesis. These include those facilitating co- and post-translational protein targeting to the cell surface, transport into and across the archaeal lipid membrane, and protein anchoring strategies. We also discuss, in some detail, the assembly of specific cell surface structures, such as the archaeal S-layer and the type IV pili. We will highlight the importance of post-translational protein modifications, such as lipid attachment and glycosylation, in the biosynthesis as well as the regulation of the functions of these cell surface structures and present the differences and similarities in the biogenesis of type IV pili across prokaryotic domains.
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Affiliation(s)
| | - Friedhelm Pfeiffer
- Computational Biology Group, Max Planck Institute of Biochemistry, 82152 Martinsried, Germany
| | - Stefan Schulze
- Department of Biology, University of Pennsylvania, Philadelphia, PA 19104, USA
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4
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Gupta S, Roy M, Ghosh A. The Archaeal Signal Recognition Particle: Present Understanding and Future Perspective. Curr Microbiol 2016; 74:284-297. [DOI: 10.1007/s00284-016-1167-9] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/25/2016] [Accepted: 11/21/2016] [Indexed: 10/20/2022]
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5
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Arbiv A, Yurist-Doutsch S, Guan Z, Eichler J. AglQ is a novel component of the Haloferax volcanii N-glycosylation pathway. PLoS One 2013; 8:e81782. [PMID: 24236216 PMCID: PMC3827465 DOI: 10.1371/journal.pone.0081782] [Citation(s) in RCA: 9] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/30/2013] [Accepted: 10/23/2013] [Indexed: 11/19/2022] Open
Abstract
N-glycosylation is a post-translational modification performed by members of all three domains of life. Studies on the halophile Haloferax volcanii have offered insight into the archaeal version of this universal protein-processing event. In the present study, AglQ was identified as a novel component of the pathway responsible for the assembly and addition of a pentasaccharide to select Asn residues of Hfx. volcanii glycoproteins, such as the S-layer glycoprotein. In cells deleted of aglQ, both dolichol phosphate, the lipid carrier used in Hfx. volcanii N-glycosylation, and modified S-layer glycoprotein Asn residues only presented the first three pentasaccharide subunits, pointing to a role for AglQ in either preparing the third sugar for attachment of the fourth pentasaccharide subunit or processing the fourth sugar prior to its addition to the lipid-linked trisaccharide. To better define the precise role of AglQ, shown to be a soluble protein, bioinformatics tools were recruited to identify sequence or structural homologs of known function. Site-directed mutagenesis experiments guided by these predictions identified residues important for AglQ function. The results obtained point to AglQ acting as an isomerase in Hfx. volcanii N-glycosylation.
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Affiliation(s)
- Adi Arbiv
- Department of Life Sciences, Ben Gurion University, Beersheva, Israel
| | | | - Ziqiang Guan
- Department of Biochemistry, Duke University Medical Center, Durham, North Carolina, United States of America
| | - Jerry Eichler
- Department of Life Sciences, Ben Gurion University, Beersheva, Israel
- * E-mail:
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6
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DNA binding in high salt: analysing the salt dependence of replication protein A3 from the halophile Haloferax volcanii. ARCHAEA (VANCOUVER, B.C.) 2012; 2012:719092. [PMID: 22973163 PMCID: PMC3438722 DOI: 10.1155/2012/719092] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Received: 05/09/2012] [Accepted: 06/18/2012] [Indexed: 11/17/2022]
Abstract
Halophilic archaea maintain intracellular salt concentrations close to saturation to survive in high-salt environments and their cellular processes have adapted to function under these conditions. Little is known regarding halophilic adaptation of the DNA processing machinery, particularly intriguing since protein-DNA interactions are classically salt sensitive. To investigate such adaptation, we characterised the DNA-binding capabilities of recombinant RPA3 from Haloferax volcanii (HvRPA3). Under physiological salt conditions (3 M KCl), HvRPA3 is monomeric, binding 18 nucleotide ssDNA with nanomolar affinity, demonstrating that RPAs containing the single OB-fold/zinc finger architecture bind with broadly comparable affinity to two OB-fold/zinc finger RPAs. Reducing the salt concentration to 1 M KCl induces dimerisation of the protein, which retains its ability to bind DNA. On circular ssDNA, two concentration-dependent binding modes are observed. Conventionally, increased salt concentration adversely affects DNA binding but HvRPA3 does not bind DNA in 0.2 M KCl, although multimerisation may occlude the binding site. The single N-terminal OB-fold is competent to bind DNA in the absence of the C-terminal zinc finger, albeit with reduced affinity. This study represents the first quantitative characterisation of DNA binding in a halophilic protein in extreme salt concentrations.
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Kuhn P, Weiche B, Sturm L, Sommer E, Drepper F, Warscheid B, Sourjik V, Koch HG. The bacterial SRP receptor, SecA and the ribosome use overlapping binding sites on the SecY translocon. Traffic 2011; 12:563-78. [PMID: 21255212 DOI: 10.1111/j.1600-0854.2011.01167.x] [Citation(s) in RCA: 56] [Impact Index Per Article: 4.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/08/2023]
Abstract
Signal recognition particle (SRP)-dependent protein targeting is a universally conserved process that delivers proteins to the bacterial cytoplasmic membrane or to the endoplasmic reticulum membrane in eukaryotes. Crucial during targeting is the transfer of the ribosome-nascent chain complex (RNC) from SRP to the Sec translocon. In eukaryotes, this step is co-ordinated by the SRβ subunit of the SRP receptor (SR), which probably senses a vacant translocon by direct interaction with the translocon. Bacteria lack the SRβ subunit and how they co-ordinate RNC transfer is unknown. By site-directed cross-linking and fluorescence resonance energy transfer (FRET) analyses, we show that FtsY, the bacterial SRα homologue, binds to the exposed C4/C5 loops of SecY, the central component of the bacterial Sec translocon. The same loops serve also as binding sites for SecA and the ribosome. The FtsY-SecY interaction involves at least the A domain of FtsY, which attributes an important function to this so far ill-defined domain. Binding of FtsY to SecY residues, which are also used by SecA and the ribosome, probably allows FtsY to sense an available translocon and to align the incoming SRP-RNC with the protein conducting channel. Thus, the Escherichia coli FtsY encompasses the functions of both the eukaryotic SRα and SRβ subunits in one single protein.
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Affiliation(s)
- Patrick Kuhn
- Institut für Biochemie und Molekularbiologie, ZBMZ, Stefan-Meier-Str. 17, D-79104 Freiburg, Germany
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8
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Archaea signal recognition particle shows the way. ARCHAEA-AN INTERNATIONAL MICROBIOLOGICAL JOURNAL 2010; 2010:485051. [PMID: 20672053 PMCID: PMC2905702 DOI: 10.1155/2010/485051] [Citation(s) in RCA: 16] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Received: 04/15/2010] [Accepted: 05/14/2010] [Indexed: 01/24/2023]
Abstract
Archaea SRP is composed of an SRP RNA molecule and two bound proteins named SRP19 and SRP54. Regulated by the binding and hydrolysis of guanosine triphosphates, the RNA-bound SRP54 protein transiently associates not only with the hydrophobic signal sequence as it emerges from the ribosomal exit tunnel, but also interacts with the membrane-associated SRP receptor (FtsY). Comparative analyses of the archaea genomes and their SRP component sequences, combined with structural and biochemical data, support a prominent role of the SRP RNA in the assembly and function of the archaea SRP. The 5e motif, which in eukaryotes binds a 72 kilodalton protein, is preserved in most archaea SRP RNAs despite the lack of an archaea SRP72 homolog. The primary function of the 5e region may be to serve as a hinge, strategically positioned between the small and large SRP domain, allowing the elongated SRP to bind simultaneously to distant ribosomal sites. SRP19, required in eukaryotes for initiating SRP assembly, appears to play a subordinate role in the archaea SRP or may be defunct. The N-terminal A region and a novel C-terminal R region of the archaea SRP receptor (FtsY) are strikingly diverse or absent even among the members of a taxonomic subgroup.
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9
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Calo D, Eichler J. Crossing the membrane in Archaea, the third domain of life. BIOCHIMICA ET BIOPHYSICA ACTA-BIOMEMBRANES 2010; 1808:885-91. [PMID: 20347718 DOI: 10.1016/j.bbamem.2010.03.020] [Citation(s) in RCA: 16] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 01/04/2010] [Revised: 03/18/2010] [Accepted: 03/18/2010] [Indexed: 11/16/2022]
Abstract
Many of the recent advancements in the field of protein translocation, particularly from the structural perspective, have relied on Archaea. For instance, the solved structures of the translocon from the methanoarchaeon Methanocaldococcus jannaschii of the ribosomal large subunit from the haloarchaeon Haloarcula marismortui and of components of the SRP pathway from several archaeal species have provided novel insight into various aspects of the translocation event. Given the major contribution that Archaea have made to our understanding of how proteins enter and traverse membranes, it is surprising that relatively little is known of protein translocation in Archaea in comparison to the well-defined translocation pathways of Eukarya and Bacteria. What is known, however, points to archaeal translocation as comprising a mosaic of eukaryal and bacterial traits together with aspects of the process seemingly unique to this, the third domain of life. Here, current understanding of archaeal protein translocation is considered. This article is part of a Special Issue entitled Protein translocation across or insertion into membranes.
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Affiliation(s)
- Doron Calo
- Department of Life Sciences, Ben Gurion University of the Negev, Beersheva 84105, Israel
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10
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Stephenson K. Sec-dependent protein translocation across biological membranes: evolutionary conservation of an essential protein transport pathway (Review). Mol Membr Biol 2009; 22:17-28. [PMID: 16092521 DOI: 10.1080/09687860500063308] [Citation(s) in RCA: 25] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/23/2022]
Abstract
All living organisms, no matter how simple or complex, possess the ability to translocate proteins across biological membranes and into different cellular compartments. Although a range of membrane transport processes exist, the major pathway used to translocate proteins across the bacterial cytoplasmic membrane or the eukaryotic endoplasmic reticulum membrane is conserved and is known as the Sec or Sec61 pathway, respectively. Over the past two decades the Sec and Sec61 pathways have been studied extensively and are well characterised at the genetic and biochemical levels. However, it is only now with the recent structural determination of a number of the key elements of the pathways that the translocation complex is beginning to give up its secrets in exquisite molecular detail. This article will focus on the routes of Sec- and Sec61-dependent membrane targeting and the nature of the translocation channel in bacteria and eukaryotes.
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Affiliation(s)
- Keith Stephenson
- School of Biochemistry and Microbiology, Leeds University, Leeds, UK.
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11
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Identification of AglE, a second glycosyltransferase involved in N glycosylation of the Haloferax volcanii S-layer glycoprotein. J Bacteriol 2008; 190:3140-6. [PMID: 18310347 PMCID: PMC2347396 DOI: 10.1128/jb.00056-08] [Citation(s) in RCA: 57] [Impact Index Per Article: 3.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022] Open
Abstract
Archaea, like Eukarya and Bacteria, are able to N glycosylate select protein targets. However, in contrast to relatively advanced understanding of the eukaryal N glycosylation process and the information being amassed on the bacterial process, little is known of this posttranslational modification in Archaea. Toward remedying this situation, the present report continues ongoing efforts to identify components involved in the N glycosylation of the Haloferax volcanii S-layer glycoprotein. By combining gene deletion together with mass spectrometry, AglE, originally identified as a homologue of murine Dpm1, was shown to play a role in the addition of the 190-Da sugar subunit of the novel pentasaccharide decorating the S-layer glycoprotein. Topological analysis of an AglE-based chimeric reporter assigns AglE as an integral membrane protein, with its N terminus and putative active site facing the cytoplasm. These finding, therefore, contribute to the developing picture of the N glycosylation pathway in Archaea.
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12
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Saunders NFW, Ng C, Raftery M, Guilhaus M, Goodchild A, Cavicchioli R. Proteomic and computational analysis of secreted proteins with type I signal peptides from the Antarctic archaeon Methanococcoides burtonii. J Proteome Res 2006; 5:2457-64. [PMID: 16944959 DOI: 10.1021/pr060220x] [Citation(s) in RCA: 30] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
Abstract
LC-MS/MS was used to identify secreted proteins in the Antarctic archaeon Methanococcoides burtonii. Seven proteins possessing a classical class 1 signal peptide were identified in the supernatant from cultures grown at 4 and 23 degrees C. The proteins included a putative S-layer cell surface protein, cell surface protein involved with cell adhesion, and trypsin-like serine protease. Protease activity was detected in the secreted fraction, and the signal peptide cleavage site of the protease was confirmed using Edman sequencing. The expression profile of putative cell surface proteins suggests a requirement for cell interactions during growth at low temperature. Sequences of the secreted proteins were used to compile a dataset containing a further 32 predicted secreted proteins from the Methanosarcinaceae. Many of these proteins were also S-layer cell surface proteins with a variety of predicted roles, particularly in cell-cell interaction. Computational analysis of signal peptides revealed a preference for lysine in the n-region, leucine in the h-region, and a eucaryal-type cleavage site, highlighting the mosaic nature of signal peptides in Archaea. This is the first study to experimentally characterize secreted proteins from a cold-adapted archaeon and provides new insight and a functional dataset for studying secretion in Archaea.
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Affiliation(s)
- Neil F W Saunders
- School of Biotechnology and Biomolecular Sciences, The University of New South Wales, Sydney, NSW 2052, Australia
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13
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Albers SV, Szabó Z, Driessen AJM. Protein secretion in the Archaea: multiple paths towards a unique cell surface. Nat Rev Microbiol 2006; 4:537-47. [PMID: 16755286 DOI: 10.1038/nrmicro1440] [Citation(s) in RCA: 59] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/28/2022]
Abstract
Archaea are similar to other prokaryotes in most aspects of cell structure but are unique with respect to the lipid composition of the cytoplasmic membrane and the structure of the cell surface. Membranes of archaea are composed of glycerol-ether lipids instead of glycerol-ester lipids and are based on isoprenoid side chains, whereas the cell walls are formed by surface-layer proteins. The unique cell surface of archaea requires distinct solutions to the problem of how proteins cross this barrier to be either secreted into the medium or assembled as appendages at the cell surface.
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Affiliation(s)
- Sonja-Verena Albers
- Department of Microbiology, Groningen Biomolecular Sciences and Biotechnology Institute and the Materials Science Centre Plus, University of Groningen, Kerklaan 30, 9751 NN Haren, The Netherlands
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14
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Pohlschröder M, Giménez MI, Jarrell KF. Protein transport in Archaea: Sec and twin arginine translocation pathways. Curr Opin Microbiol 2005; 8:713-9. [PMID: 16257258 DOI: 10.1016/j.mib.2005.10.006] [Citation(s) in RCA: 52] [Impact Index Per Article: 2.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/18/2005] [Accepted: 10/11/2005] [Indexed: 12/01/2022]
Abstract
The transport of proteins into and across hydrophobic membranes is an essential cellular process. The majority of proteins that are translocated in an unfolded conformation traverse the membrane by way of the universally conserved Sec pathway, whereas the twin arginine translocation pathway is responsible for the transport of folded proteins across the membrane. Structural, biochemical and genetic analyses of these processes in Archaea have revealed unique archaeal features, and have also provided a better understanding of these pathways in organisms of all domains. Further study of these pathways in Archaea might elucidate fundamental principles involved in each type of transport and could help determine their relative costs and benefits as well as evolutionary adaptations in protein secretion strategies.
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15
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Hasona A, Crowley PJ, Levesque CM, Mair RW, Cvitkovitch DG, Bleiweis AS, Brady LJ. Streptococcal viability and diminished stress tolerance in mutants lacking the signal recognition particle pathway or YidC2. Proc Natl Acad Sci U S A 2005; 102:17466-71. [PMID: 16293689 PMCID: PMC1297686 DOI: 10.1073/pnas.0508778102] [Citation(s) in RCA: 85] [Impact Index Per Article: 4.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/18/2022] Open
Abstract
The signal recognition particle (SRP)-translocation pathway is conserved in all three domains of life and delivers membrane and secretory proteins to the cytoplasmic membrane or endoplasmic reticulum. We determined the requirement in the cariogenic oral pathogen Streptocococcus mutans of the three universally conserved elements of the SRP pathway: Ffh/SRP54, scRNA, and FtsY/SRalpha. Previously, we reported that insertional interruption of S. mutans ffh was not lethal, but resulted in acid sensitivity. To test whether S. mutans could survive extensive disruption of the SRP pathway, single and double deletions of genes encoding Ffh, scRNA, and FtsY were generated. Without environmental stressors, all mutant strains were viable, but unlike the wild-type, none could initiate growth at pH 5.0 or in 3.5% NaCl. Survival of challenge with 0.3 mM H(2)O(2) was also diminished without ffh. Members of the YidC/Oxa1/Alb3 family are also ubiquitous, involved in the translocation and assembly of membrane proteins, and have been identified in prokaryotes/mitochondria/chloroplasts. Two genes encoding YidC homologs, YidC1 and YidC2, are present in streptococcal genomes with both expressed in S. mutans. Deletion of YidC1 demonstrated no obvious phenotype. Elimination of YidC2 resulted in a stress-sensitive phenotype similar to SRP pathway mutants. Mutants lacking both YidC2 and SRP components were severely impaired and barely able to grow, even in the absence of environmental stress. Here, we report the dispensability of the cotranslational SRP protein translocation system in a bacterium. In S. mutans, this pathway contributes to protection against rapid environmental challenge and may overlap functionally with YidC2.
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Affiliation(s)
- Adnan Hasona
- Department of Oral Biology, University of Florida, Gainesville, FL 32610, USA
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16
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Pohlschröder M, Hartmann E, Hand NJ, Dilks K, Haddad A. DIVERSITY AND EVOLUTION OF PROTEIN TRANSLOCATION. Annu Rev Microbiol 2005; 59:91-111. [PMID: 16153164 DOI: 10.1146/annurev.micro.59.030804.121353] [Citation(s) in RCA: 87] [Impact Index Per Article: 4.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/09/2022]
Abstract
Cells need to translocate proteins into and across hydrophobic membranes in order to interact with the extracellular environment. Although a subset of proteins are thought to spontaneously insert into lipid bilayers, translocation of most transported proteins requires additional cellular components. Such components catalyze efficient lateral transport into or across cellular membranes in prokaryotes and eukaryotes. These include, among others, the conserved YidC/Oxa1/Alb3 proteins as well as components of the Sec and the Tat pathways. Our current knowledge of the function and distribution of these components and their corresponding pathways in organisms of the three domains of life is reviewed. On the basis of this information, the evolution of protein translocation is discussed.
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Affiliation(s)
- Mechthild Pohlschröder
- Department of Biology, University of Pennsylvania, Philadelphia, Pennsylvania 19104, USA.
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17
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Hutcheon GW, Vasisht N, Bolhuis A. Characterisation of a highly stable alpha-amylase from the halophilic archaeon Haloarcula hispanica. Extremophiles 2005; 9:487-95. [PMID: 16075161 DOI: 10.1007/s00792-005-0471-2] [Citation(s) in RCA: 86] [Impact Index Per Article: 4.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/21/2005] [Accepted: 06/20/2005] [Indexed: 10/25/2022]
Abstract
Intracellular and extracellular proteins from halophilic archaea face very saline conditions and must be able to maintain stability and functionality at nearly saturated salt concentrations. Haloarchaeal proteins contain specific adaptations to prevent aggregation and loss of activity in such conditions, but these adaptations usually result in a lack of stability in the absence of salt. Here, we present the characterisation of a secreted alpha-amylase (AmyH) from the halophilic archaeon Haloarcula hispanica. AmyH was shown to be very halophilic but, unusually for a halophilic protein, it retained activity in the absence of salt. Intrinsic fluorescence measurements and activity assays showed that AmyH was very stable in high-salt buffer and even maintained stability upon the addition of urea. Urea-induced denaturation was only achieved in the absence of NaCl, demonstrating clearly that the stability of the protein was salt-dependent. Sequencing of the amyH gene showed an amino acid composition typical of halophilic proteins and, moreover, the presence of a signal peptide containing diagnostic features characteristic of export via the Twin-arginine translocase (Tat). Analysis of the export of AmyH showed that it was translocated post-translationally, most likely in a folded and active conformation, confirming that AmyH is a substrate of the Tat pathway.
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Affiliation(s)
- George W Hutcheon
- Department of Biological Sciences, University of Warwick, CV4 7AL, Coventry, UK
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18
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Haddad A, Rose RW, Pohlschröder M. The Haloferax volcanii FtsY homolog is critical for haloarchaeal growth but does not require the A domain. J Bacteriol 2005; 187:4015-22. [PMID: 15937164 PMCID: PMC1151737 DOI: 10.1128/jb.187.12.4015-4022.2005] [Citation(s) in RCA: 21] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022] Open
Abstract
The targeting of many Sec substrates to the membrane-associated translocation pore requires the cytoplasmic signal recognition particle (SRP). In Eukarya and Bacteria it has been shown that membrane docking of the SRP-substrate complex occurs via the universally conserved SRP receptor (Sralpha/beta and FtsY, respectively). While much has been learned about the archaeal SRP in recent years, few studies have examined archaeal Sralpha/FtsY homologs. In the present study the FtsY homolog of Haloferax volcanii was characterized in its native host. Disruption of the sole chromosomal copy of ftsY in H. volcanii was possible only under conditions where either the full-length haloarchaeal FtsY or an amino-terminally truncated version of this protein lacking the A domain, was expressed in trans. Subcellular fractionation analysis of H. volcanii ftsY deletion strains expressing either one of the complementing proteins revealed that in addition to a cytoplasmic pool, both proteins cofractionate with the haloarchaeal cytoplasmic membrane. Moreover, membrane localization of the universally conserved SRP subunit SRP54, the key binding partner of FtsY, was detected in both H. volcanii strains. These analyses suggest that the H. volcanii FtsY homolog plays a crucial role but does not require its A domain for haloarchaeal growth.
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Affiliation(s)
- Alex Haddad
- Department of Biology, University of Pennsylvania, Philadelphia 19104, USA
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Ring G, Eichler J. In the Archaea Haloferax volcanii, Membrane Protein Biogenesis and Protein Synthesis Rates Are Affected by Decreased Ribosomal Binding to the Translocon. J Biol Chem 2004; 279:53160-6. [PMID: 15475349 DOI: 10.1074/jbc.m410590200] [Citation(s) in RCA: 16] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022] Open
Abstract
In the haloarchaea Haloferax volcanii, ribosomes are found in the cytoplasm and membrane-bound at similar levels. Transformation of H. volcanii to express chimeras of the translocon components SecY and SecE fused to a cellulose-binding domain substantially decreased ribosomal membrane binding, relative to non-transformed cells, likely due to steric hindrance by the cellulose-binding domain. Treatment of cells with the polypeptide synthesis terminator puromycin, with or without low salt washes previously shown to prevent in vitro ribosomal membrane binding in halophilic archaea, did not lead to release of translocon-bound ribosomes, indicating that ribosome release is not directly related to the translation status of a given ribosome. Release was, however, achieved during cell starvation or stationary growth, pointing at a regulated manner of ribosomal release in H. volcanii. Decreased ribosomal binding selectively affected membrane protein levels, suggesting that membrane insertion occurs co-translationally in Archaea. In the presence of chimera-incorporating sterically hindered translocons, the reduced ability of ribosomes to bind in the transformed cells modulated protein synthesis rates over time, suggesting that these cells manage to compensate for the reduction in ribosome binding. Possible strategies for this compensation, such as a shift to a post-translational mode of membrane protein insertion or maintained ribosomal membrane-binding, are discussed.
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Affiliation(s)
- Gabriela Ring
- Department of Life Sciences, Ben Gurion University, Beersheva 84105, Israel
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