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Abstract
Signal peptidases are the membrane bound enzymes that cleave off the amino-terminal signal peptide from secretory preproteins . There are two types of bacterial signal peptidases . Type I signal peptidase utilizes a serine/lysine catalytic dyad mechanism and is the major signal peptidase in most bacteria. Type II signal peptidase is an aspartic protease specific for prolipoproteins. This chapter will review what is known about the structure, function and mechanism of these unique enzymes.
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Affiliation(s)
- Mark Paetzel
- Department of Molecular Biology and Biochemistry, Simon Fraser University, South Science Building 8888 University Drive, Burnaby, BC, V5A 1S6, Canada.
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2
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Crane JM, Randall LL. The Sec System: Protein Export in Escherichia coli. EcoSal Plus 2017; 7:10.1128/ecosalplus.ESP-0002-2017. [PMID: 29165233 PMCID: PMC5807066 DOI: 10.1128/ecosalplus.esp-0002-2017] [Citation(s) in RCA: 61] [Impact Index Per Article: 8.7] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/22/2017] [Indexed: 11/20/2022]
Abstract
In Escherichia coli, proteins found in the periplasm or the outer membrane are exported from the cytoplasm by the general secretory, Sec, system before they acquire stably folded structure. This dynamic process involves intricate interactions among cytoplasmic and membrane proteins, both peripheral and integral, as well as lipids. In vivo, both ATP hydrolysis and proton motive force are required. Here, we review the Sec system from the inception of the field through early 2016, including biochemical, genetic, and structural data.
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Affiliation(s)
- Jennine M. Crane
- Department of Biochemistry, University of Missouri, Columbia, Missouri
| | - Linda L. Randall
- Department of Biochemistry, University of Missouri, Columbia, Missouri
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3
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Paetzel M. Structure and mechanism of Escherichia coli type I signal peptidase. BIOCHIMICA ET BIOPHYSICA ACTA-MOLECULAR CELL RESEARCH 2013; 1843:1497-508. [PMID: 24333859 DOI: 10.1016/j.bbamcr.2013.12.003] [Citation(s) in RCA: 54] [Impact Index Per Article: 4.9] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Received: 08/25/2013] [Revised: 11/26/2013] [Accepted: 12/04/2013] [Indexed: 12/16/2022]
Abstract
Type I signal peptidase is the enzyme responsible for cleaving off the amino-terminal signal peptide from proteins that are secreted across the bacterial cytoplasmic membrane. It is an essential membrane bound enzyme whose serine/lysine catalytic dyad resides on the exo-cytoplasmic surface of the bacterial membrane. This review discusses the progress that has been made in the structural and mechanistic characterization of Escherichia coli type I signal peptidase (SPase I) as well as efforts to develop a novel class of antibiotics based on SPase I inhibition. This article is part of a Special Issue entitled: Protein trafficking and secretion in bacteria. Guest Editors: Anastassios Economou and Ross Dalbey.
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Affiliation(s)
- Mark Paetzel
- Department of Molecular Biology and Biochemistry, Simon Fraser University, 8888 University Drive, Burnaby, British Columbia V5A 1S6, Canada.
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4
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Abstract
Understanding the transport of hydrophilic proteins across biological membranes continues to be an important undertaking. The general secretory (Sec) pathway in Escherichia coli transports the majority of E. coli proteins from their point of synthesis in the cytoplasm to their sites of final localization, associating sequentially with a number of protein components of the transport machinery. The targeting signals for these substrates must be discriminated from those of proteins transported via other pathways. While targeting signals for each route have common overall characteristics, individual signal peptides vary greatly in their amino acid sequences. How do these diverse signals interact specifically with the proteins that comprise the appropriate transport machinery and, at the same time, avoid targeting to an alternate route? The recent publication of the crystal structures of components of the Sec transport machinery now allows a more thorough consideration of the interactions of signal sequences with these components.
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Affiliation(s)
| | - Debra A. Kendall
- To whom correspondence should be addressed. Mailing address: Department of Molecular and Cell Biology, 91 North Eagleville Road, The University of Connecticut, Storrs, CT 06269-3125. Phone: (860) 486-1891. Fax: (860) 486-4331. E-mail:
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5
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van Dalen A, de Kruijff B. The role of lipids in membrane insertion and translocation of bacterial proteins. BIOCHIMICA ET BIOPHYSICA ACTA-MOLECULAR CELL RESEARCH 2005; 1694:97-109. [PMID: 15546660 DOI: 10.1016/j.bbamcr.2004.03.007] [Citation(s) in RCA: 53] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 10/24/2003] [Revised: 02/03/2004] [Accepted: 03/01/2004] [Indexed: 11/20/2022]
Abstract
Phospholipids are essential building blocks of membranes and maintain the membrane permeability barrier of cells and organelles. They provide not only the bilayer matrix in which the functional membrane proteins reside, but they also can play direct roles in many essential cellular processes. In this review, we give an overview of the lipid involvement in protein translocation across and insertion into the Escherichia coli inner membrane. We describe the key and general roles that lipids play in these processes in conjunction with the protein components involved. We focus on the Sec-mediated insertion of leader peptidase. We describe as well the more direct roles that lipids play in insertion of the small coat proteins Pf3 and M13. Finally, we focus on the role of lipids in membrane assembly of oligomeric membrane proteins, using the potassium channel KcsA as model protein. In all cases, the anionic lipids and lipids with small headgroups play important roles in either determining the efficiency of the insertion and assembly process or contributing to the directionality of the insertion process.
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Affiliation(s)
- Annemieke van Dalen
- Department Biochemistry of Membranes, Centre for Biomembranes and Lipid Enzymology, Institute of Biomembranes, Utrecht University, Padualaan 8, 3584 CH Utrecht, The Netherlands
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6
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van Roosmalen ML, Geukens N, Jongbloed JDH, Tjalsma H, Dubois JYF, Bron S, van Dijl JM, Anné J. Type I signal peptidases of Gram-positive bacteria. BIOCHIMICA ET BIOPHYSICA ACTA-MOLECULAR CELL RESEARCH 2005; 1694:279-97. [PMID: 15546672 DOI: 10.1016/j.bbamcr.2004.05.006] [Citation(s) in RCA: 110] [Impact Index Per Article: 5.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 10/24/2003] [Accepted: 05/12/2004] [Indexed: 11/21/2022]
Abstract
Proteins that are exported from the cytoplasm to the periplasm and outer membrane of Gram-negative bacteria, or the cell wall and growth medium of Gram-positive bacteria, are generally synthesized as precursors with a cleavable signal peptide. During or shortly after pre-protein translocation across the cytoplasmic membrane, the signal peptide is removed by signal peptidases. Importantly, pre-protein processing by signal peptidases is essential for bacterial growth and viability. This review is focused on the signal peptidases of Gram-positive bacteria, Bacillus and Streptomyces species in particular. Evolutionary concepts, current knowledge of the catalytic mechanism, substrate specificity requirements and structural aspects are addressed. As major insights in signal peptidase function and structure have been obtained from studies on the signal peptidase LepB of Escherichia coli, similarities and differences between this enzyme and known Gram-positive signal peptidases are highlighted. Notably, while the incentive for previous research on Gram-positive signal peptidases was largely based on their role in the biotechnologically important process of protein secretion, present-day interest in these essential enzymes is primarily derived from the idea that they may serve as targets for novel anti-microbials.
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Affiliation(s)
- Maarten L van Roosmalen
- Department of Genetics, Groningen Biomolecular Sciences and Biotechnology Institute, University of Groningen, Kerklaan 30, 9751 NN Haren, Netherlands
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7
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Kol MA, van Dalen A, de Kroon AIPM, de Kruijff B. Translocation of phospholipids is facilitated by a subset of membrane-spanning proteins of the bacterial cytoplasmic membrane. J Biol Chem 2003; 278:24586-93. [PMID: 12714595 DOI: 10.1074/jbc.m301875200] [Citation(s) in RCA: 63] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022] Open
Abstract
The mechanism by which phospholipids are transported across biogenic membranes, such as the bacterial cytoplasmic membrane, is unknown. We hypothesized that this process is mediated by the presence of the membrane-spanning segments of inner membrane proteins, rather than by dedicated flippases. In support of the hypothesis, it was demonstrated that transmembrane alpha-helical peptides, mimicking the membrane-spanning segments, mediate flop of 2-6-(7-nitro-2,1,3-benzoxadiazol-4-yl) aminocaproyl (C6-NBD)-phospholipids (Kol, M. A., de Kroon, A. I., Rijkers, D. T., Killian, J. A., and de Kruijff, B. (2001) Biochemistry 40, 10500-10506). Here the dithionite reduction assay was used to measure transbilayer equilibration of C6-NBD-phospholipids in proteoliposomes, composed of Escherichia coli phospholipids and a subset of bacterial membrane proteins. It is shown that two well characterized integral proteins of the bacterial cytoplasmic membrane, leader peptidase and the potassium channel KcsA, induce phospholipid translocation, most likely by their transmembrane domains. In contrast, the ATP-binding cassette transporter from the E. coli inner membrane MsbA, a putative lipid flippase, did not mediate phospholipid translocation, irrespective of the presence of ATP. OmpT, an outer membrane protein from E. coli, did not facilitate flop either, demonstrating specificity of protein-mediated phospholipid translocation. The results are discussed in the light of phospholipid transport across the E. coli inner membrane.
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Affiliation(s)
- Matthijs A Kol
- Department Biochemistry of Membranes, Centre for Biomembranes and Lipid Enzymology, Institute of Biomembranes, Utrecht University, Padualaan 8, The Netherlands.
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Urbanus ML, Fröderberg L, Drew D, Björk P, de Gier JWL, Brunner J, Oudega B, Luirink J. Targeting, insertion, and localization of Escherichia coli YidC. J Biol Chem 2002; 277:12718-23. [PMID: 11821429 DOI: 10.1074/jbc.m200311200] [Citation(s) in RCA: 72] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022] Open
Abstract
YidC was recently shown to play an important role in the assembly of inner membrane proteins (IMPs) both in conjunction with and separate from the Sec-translocon. Little is known about the biogenesis and structural and functional properties of YidC, itself a polytopic IMP. Here we analyze the targeting and membrane integration of YidC using in vivo and in vitro approaches. The combined data indicate that YidC is targeted by the signal recognition particle and inserts at the SecAYEG-YidC translocon early during biogenesis, unlike its mitochondrial homologue Oxa1p. In addition, YidC is shown to be relatively abundant compared with other components involved in IMP assembly and is predominantly localized at the poles of the cell.
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Affiliation(s)
- Malene L Urbanus
- Department of Microbiology, Institute for Molecular Biological Sciences, De Boelelaan 1087, 1081 HV Amsterdam, The Netherlands
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9
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Fan F, Lunsford RD, Sylvester D, Fan J, Celesnik H, Iordanescu S, Rosenberg M, McDevitt D. Regulated ectopic expression and allelic-replacement mutagenesis as a method for gene essentiality testing in Staphylococcus aureus. Plasmid 2001; 46:71-5. [PMID: 11535039 DOI: 10.1006/plas.2001.1526] [Citation(s) in RCA: 30] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022]
Abstract
Conditional expression systems were utilized for the ectopic induction of essential genes in Staphylococcus aureus. Resulting strains were then subjected to allelic-replacement mutagenesis of the native allele under inducing conditions for expression of the ectopic copy of the gene. This strategy produced test strains whereby cellular viability was uniquely dependent on the presence of inducer and provided a direct and absolute confirmation of genetic essentiality for each locus. The procedure is particularly useful for genes that are difficult to analyze by conventional inactivation strategies due to either small size or complex genomic organization.
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Affiliation(s)
- F Fan
- Antimicrobials and Host Defense CEDD, Collegeville, Pennsylvania 19426, USA.
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10
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Paetzel M, Dalbey RE, Strynadka NC. The structure and mechanism of bacterial type I signal peptidases. A novel antibiotic target. Pharmacol Ther 2000; 87:27-49. [PMID: 10924740 DOI: 10.1016/s0163-7258(00)00064-4] [Citation(s) in RCA: 118] [Impact Index Per Article: 4.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/23/2022]
Abstract
Type I signal peptidases are essential membrane-bound serine proteases that function to cleave the amino-terminal signal peptide extension from proteins that are translocated across biological membranes. The bacterial signal peptidases are unique serine proteases that utilize a Ser/Lys catalytic dyad mechanism in place of the classical Ser/His/Asp catalytic triad mechanism. They represent a potential novel antibiotic target at the bacterial membrane surface. This review will discuss the bacterial signal peptidases that have been characterized to date, as well as putative signal peptidase sequences that have been recognized via bacterial genome sequencing. We review the investigations into the mechanism of Escherichia coli and Bacillus subtilis signal peptidase, and discuss the results in light of the recent crystal structure of the E. coli signal peptidase in complex with a beta-lactam-type inhibitor. The proposed conserved structural features of Type I signal peptidases give additional insight into the mechanism of this unique enzyme.
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Affiliation(s)
- M Paetzel
- Department of Biochemistry and Molecular Biology, Faculty of Medicine, University of British Columbia, Vancouver, BC, Canada
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11
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van Dalen A, Killian A, de Kruijff B. Delta psi stimulates membrane translocation of the C-terminal part of a signal sequence. J Biol Chem 1999; 274:19913-8. [PMID: 10391938 DOI: 10.1074/jbc.274.28.19913] [Citation(s) in RCA: 22] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022] Open
Abstract
For several proteins in Escherichia coli it has been shown that the protonmotive force (pmf) dependence of translocation can be varied with the signal sequence composition, suggesting an effect of the pmf on the signal sequence. To test this possibility, we analyzed the effect of the membrane potential on translocation of the signal sequence. For this purpose, a precursor peptide was used (SP+7), corresponding to the signal sequence of PhoE with the first seven amino acids of the mature part that can be processed by purified leader peptidase. Translocation was studied in pure lipid vesicles containing leader peptidase, with its active site inside the vesicles. In the presence of a positive inside Delta psi, the amount of processing of SP+7 was significantly higher than without a Delta psi, indicating that the translocation of the cleavage region is stimulated by Delta psi. Replacement of the helix-breaking glycine residue at position -10 in the signal sequence for a leucine abolished the effect of Delta psi on the translocation of the cleavage region. It is concluded that Delta psi directly acts on the wild type signal sequence by stimulating the translocation of its C terminus. We propose that Delta psi acts on the signal sequence by stretching it into a transmembrane orientation.
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Affiliation(s)
- A van Dalen
- Department of Biochemistry of Membranes, Centre for Biomembranes and Lipid Enzymology, Institute of Biomembranes, Utrecht University, Padualaan 8, 3584 CH Utrecht, The Netherlands.
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12
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van Klompenburg W, Ridder AN, van Raalte AL, Killian AJ, von Heijne G, de Kruijff B. In vitro membrane integration of leader peptidase depends on the Sec machinery and anionic phospholipids and can occur post-translationally. FEBS Lett 1997; 413:109-14. [PMID: 9287126 DOI: 10.1016/s0014-5793(97)00888-0] [Citation(s) in RCA: 23] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/05/2023]
Abstract
A cell-free system based on a lysate and membrane vesicles from Escherichia coli is used to study characteristics of the membrane integration reaction of the polytopic membrane protein leader peptidase (Lep). Integration into inverted inner membrane vesicles was detected by partial protection against externally added protease. Integration is most efficient when coupled to translation but can also occur post-translationally and depends on the action of the proteinaceous Sec machinery and availability of anionic phospholipids. Lep is the first example of a membrane protein without cleavable signal sequence which requires anionic lipids for integration in vitro.
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Affiliation(s)
- W van Klompenburg
- Department of Biochemistry of Membranes, Centre for Biomembranes and Lipid Enzymology, Utrecht University, The Netherlands.
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13
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van Klompenburg W, Nilsson I, von Heijne G, de Kruijff B. Anionic phospholipids are determinants of membrane protein topology. EMBO J 1997; 16:4261-6. [PMID: 9250669 PMCID: PMC1170051 DOI: 10.1093/emboj/16.14.4261] [Citation(s) in RCA: 169] [Impact Index Per Article: 6.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/05/2023] Open
Abstract
The orientation of many membrane proteins is determined by the asymmetric distribution of positively charged amino acid residues in cytoplasmic and translocated loops. The positive-inside rule states that loops with large amounts of these residues tend to have cytoplasmic locations. Orientations of constructs derived from the inner membrane protein leader peptidase from Escherichia coli were found to depend on the anionic phospholipid content of the membrane. Lowering the contents of anionic phospholipids facilitated membrane passage of positively charged loops. On the other hand, elevated contents of acidic phospholipids in the membrane rendered translocation more sensitive to positively charged residues. The results demonstrate that anionic lipids are determinants of membrane protein topology and suggest that interactions between negatively charged phospholipids and positively charged amino acid residues contribute to the orientation of membrane proteins.
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Affiliation(s)
- W van Klompenburg
- Department of Biochemistry of Membranes, Centre for Biomembranes and Lipid Enzymology, Utrecht University, The Netherlands
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14
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Cregg KM, Wilding I, Black MT. Molecular cloning and expression of the spsB gene encoding an essential type I signal peptidase from Staphylococcus aureus. J Bacteriol 1996; 178:5712-8. [PMID: 8824617 PMCID: PMC178411 DOI: 10.1128/jb.178.19.5712-5718.1996] [Citation(s) in RCA: 92] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/02/2023] Open
Abstract
The gene, spsB, encoding a type I signal peptidase has been cloned from the gram-positive eubacterium Staphylococcus aureus. The gene encodes a protein of 191 amino acid residues with a calculated molecular mass of 21,692 Da. Comparison of the protein sequence with those of known type I signal peptidases indicates conservation of amino acid residues known to be important or essential for catalytic activity. The enzyme has been expressed to high levels in Escherichia coli and has been demonstrated to possess enzymatic activity against E. coli preproteins in vivo. Experiments whereby the spsB gene was transferred to a plasmid that is temperature sensitive for replication indicate that spsB is an essential gene. We identified an open reading frame immediately upstream of the spsB gene which encodes a type I signal peptidase homolog of 174 amino acid residues with a calculated molecular mass of 20,146 Da that is predicted to be devoid of catalytic activity.
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Affiliation(s)
- K M Cregg
- Biotechnology, SmithKline Beecham Pharmaceuticals, Epsom, Surrey, United Kingdom
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15
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Huijbregts RP, de Kroon AI, de Kruijff B. Rapid transmembrane movement of C6-NBD-labeled phospholipids across the inner membrane of Escherichia coli. BIOCHIMICA ET BIOPHYSICA ACTA 1996; 1280:41-50. [PMID: 8634315 DOI: 10.1016/0005-2736(95)00272-3] [Citation(s) in RCA: 32] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 02/01/2023]
Abstract
In this study we have investigated the transmembrane movement of short chain fluorescently labeled phospholipids across the inner membrane of Escherichia coli. Exogenously added C6-NBD-labeled phospholipids rapidly flip across the inner membrane of E. coli, as was shown by a dithionite reduction assay applied to inverted inner membrane vesicles (IIMV) isolated from wild type E. coli cells. The rate of transmembrane movement of the phospholipid probes incorporated into IIMV is temperature dependent, and shows no phospholipid head group specificity. C6-NBD-labeled phospholipids translocate across the membrane of IIMV incubated at 37 degrees C with a t1/2 of 7 min. After the incorporation into IIMV C6-NBD-PG is partially converted to CL by CL-synthase. If IIMV are pretreated with proteinase K the conversion of this fluorescent probe to C6-NBD-CL is not observed anymore, suggesting that the catalytic domain of CL-synthase is at the cytoplasmic site of the plasma membrane of E. coli. Newly synthesized C6-NBD-CL also flips across the inner membrane although at a slower rate than the other phospholipid probes. The transmembrane movement occurs in both directions and is not influenced by treatment of the IIMV with a sulfhydryl reagent or a proteinase, nor by the presence of ATP, or a deltapH across the membrane of the IIMV. However, the transmembrane movement of the C6-NBD-labeled phospholipid probes is not observed in LUVETs (large unilamellar vesicles made by extrusion technique) prepared of wild type E. coli lipids, indicating that the rapid transmembrane movement of phospholipids across the inner membrane of E. coli is a protein-mediated process.
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Affiliation(s)
- R P Huijbregts
- Department Biochemistry of Membranes, Centre for Biomembranes and Lipid Enzymology, Institute of Biomembranes, Utrecht University, The Netherlands
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