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Tian W, Naveed H, Lin M, Liang J. GeTFEP: A general transfer free energy profile of transmembrane proteins. Protein Sci 2019; 29:469-479. [PMID: 31658402 DOI: 10.1002/pro.3763] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/10/2019] [Revised: 10/20/2019] [Accepted: 10/23/2019] [Indexed: 01/06/2023]
Abstract
Free energy of transferring amino acid side-chains from aqueous environment into lipid bilayers, known as transfer free energy (TFE), provides important information on the thermodynamic stability of membrane proteins. In this study, we derived a TFE profile named General Transfer Free Energy Profile (GeTFEP) based on computation of the TFEs of 58 β-barrel membrane proteins (βMPs). The GeTFEP agrees well with experimentally measured and computationally derived TFEs. Analysis based on the GeTFEP shows that residues in different regions of the transmembrane (TM) segments of βMPs have different roles during the membrane insertion process. Results further reveal the importance of the sequence pattern of TM strands in stabilizing βMPs in the membrane environment. In addition, we show that GeTFEP can be used to predict the positioning and the orientation of βMPs in the membrane. We also show that GeTFEP can be used to identify structurally or functionally important amino acid residue sites of βMPs. Furthermore, the TM segments of α-helical membrane proteins can be accurately predicted with GeTFEP, suggesting that the GeTFEP is of general applicability in studying membrane protein.
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Affiliation(s)
- Wei Tian
- Department of Bioengineering, University of Illinois at Chicago, Chicago, Illinois
| | - Hammad Naveed
- Department of Computer Science, National University of Computer and Emerging Sciences (NUCES-FAST), Islamabad, Islamabad Capital Territory, Pakistan
| | - Meishan Lin
- Department of Bioengineering, University of Illinois at Chicago, Chicago, Illinois
| | - Jie Liang
- Department of Bioengineering, University of Illinois at Chicago, Chicago, Illinois
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2
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Bakholdina SI, Tischenko NM, Sidorin EV, Isaeva MP, Likhatskaya GN, Dmitrenok PS, Kim NY, Chernikov OV, Solov'eva TF. Recombinant Phospholipase A1 of the Outer Membrane of Psychrotrophic Yersinia pseudotuberculosis: Expression, Purification, and Characterization. BIOCHEMISTRY (MOSCOW) 2016; 81:47-57. [PMID: 26885582 DOI: 10.1134/s0006297916010053] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 01/23/2023]
Abstract
The pldA gene encoding membrane-bound phospholipase A1 of Yersinia pseudotuberculosis was cloned and expressed in Escherichia coli cells. Recombinant phospholipase A1 (rPldA) was isolated from inclusion bodies dissolved in 8 M urea by two-stage chromatography (ion-exchange and gel-filtration chromatography) as an inactive monomer. The molecular mass of the rPldA determined by MALDI-TOF MS was 31.7 ± 0.4 kDa. The highly purified rPldA was refolded by 10-fold dilution with buffer containing 10 mM Triton X-100 and subsequent incubation at room temperature for 16 h. The refolded rPldA hydrolyzed 1,2-dioleoyl-sn-glycero-3-phosphatidylcholine in the presence of calcium ions. The enzyme exhibited maximal activity at 37°C and nearly 40% of maximal activity at 15°C. The phospholipase A1 was active over a wide range of pH from 4 to 11, exhibiting maximal activity at pH 10. Spatial structure models of the monomer and the dimer of Y. pseudotuberculosis phospholipase A1 were constructed, and functionally important amino acid residues of the enzyme were determined. Structural differences between phospholipases A1 from Y. pseudotuberculosis and E. coli, which can affect the functional activity of the enzyme, were revealed.
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Affiliation(s)
- S I Bakholdina
- Elyakov Pacific Institute of Bioorganic Chemistry, Russian Academy of Sciences, Far East Branch, Vladivostok, 690022, Russia.
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3
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Lin M, Gessmann D, Naveed H, Liang J. Outer Membrane Protein Folding and Topology from a Computational Transfer Free Energy Scale. J Am Chem Soc 2016; 138:2592-601. [PMID: 26860422 DOI: 10.1021/jacs.5b10307] [Citation(s) in RCA: 22] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/16/2022]
Abstract
Knowledge of the transfer free energy of amino acids from aqueous solution to a lipid bilayer is essential for understanding membrane protein folding and for predicting membrane protein structure. Here we report a computational approach that can calculate the folding free energy of the transmembrane region of outer membrane β-barrel proteins (OMPs) by combining an empirical energy function with a reduced discrete state space model. We quantitatively analyzed the transfer free energies of 20 amino acid residues at the center of the lipid bilayer of OmpLA. Our results are in excellent agreement with the experimentally derived hydrophobicity scales. We further exhaustively calculated the transfer free energies of 20 amino acids at all positions in the TM region of OmpLA. We found that the asymmetry of the Gram-negative bacterial outer membrane as well as the TM residues of an OMP determine its functional fold in vivo. Our results suggest that the folding process of an OMP is driven by the lipid-facing residues in its hydrophobic core, and its NC-IN topology is determined by the differential stabilities of OMPs in the asymmetrical outer membrane. The folding free energy is further reduced by lipid A and assisted by general depth-dependent cooperativities that exist between polar and ionizable residues. Moreover, context-dependency of transfer free energies at specific positions in OmpLA predict regions important for protein function as well as structural anomalies. Our computational approach is fast, efficient and applicable to any OMP.
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Affiliation(s)
- Meishan Lin
- Department of Bioengineering, University of Illinois at Chicago , Chicago, Illinois 60607, United States
| | - Dennis Gessmann
- Department of Bioengineering, University of Illinois at Chicago , Chicago, Illinois 60607, United States
| | - Hammad Naveed
- Department of Bioengineering, University of Illinois at Chicago , Chicago, Illinois 60607, United States
| | - Jie Liang
- Department of Bioengineering, University of Illinois at Chicago , Chicago, Illinois 60607, United States
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4
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Belosludtsev KN, Belosludtseva NV, Kondratyev MS, Agafonov AV, Purtov YA. Interaction of phospholipase A of the E. coli outer membrane with the inhibitors of eucaryotic phospholipases A₂ and their effect on the Ca²⁺-induced permeabilization of the bacterial membrane. J Membr Biol 2014; 247:281-8. [PMID: 24477786 DOI: 10.1007/s00232-014-9633-4] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/29/2013] [Accepted: 01/13/2014] [Indexed: 02/03/2023]
Abstract
Phospholipase A of the bacterial outer membrane (OMPLA) is a β-barrel membrane protein which is activated under various stress conditions. The current study examines interaction of inhibitors of eucaryotic phospholipases A₂--palmitoyl trifluoromethyl ketone (PACOCF₃) and aristolochic acid (AA)--with OMPLA and considers a possible involvement of the enzyme in the Ca²⁺-dependent permeabilization of the outer membrane of Escherichia coli. Using the method of molecular docking, it has been predicted that PACOCF₃ and AA bind to OMPLA at the same site and with the same affinity as the OMPLA inhibitors, hexadecanesulfonylfluoride and bromophenacyl bromide, and the substrate of the enzyme palmitoyl oleoyl phosphatidylethanolamine. It has also been shown that PACOCF₃, AA, and bromophenacyl bromide inhibit the Ca²⁺-induced temperature-dependent changes in the permeability of the bacterial membrane for the fluorescent probe propidium iodide and suppressed the transformation of E. coli cells with plasmid DNA induced by Ca²⁺ and heat shock. The cell viability was not affected by the eucaryotic phospholipases A₂ inhibitors. The study discusses a possible involvement of OMPLA in the mechanisms of bacterial transmembrane transport based on the permeabilization of the bacterial outer membrane.
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Affiliation(s)
- Konstantin N Belosludtsev
- Institute of Theoretical and Experimental Biophysics RAS, Institutskaya, 3, Pushchino, Moscow Region, 142290, Russia,
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5
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Abstract
Phospholipids are present in all living organisms. They are a major component of all biological membranes, along with glycolipids and cholesterol. Enzymes aimed at cleaving the various bonds in phospholipids, namely phospholipases, are consequently widespread in nature, playing very diverse roles from aggression in snake venom to signal transduction, lipid mediators production, and digestion in humans. Although all phospholipases target phospholipids as substrates, they vary in the site of action on the phospholipids molecules, physiological function, mode of action, and their regulation. Significant studies on phospholipases characterization, physiological role, and industrial potential have been conducted worldwide. Some of them have been directed for biotechnological advances, such as gene discovery and functional enhancement by protein engineering. Others reported phospholipases as virulence factors and major causes of pathophysiological effects. In this introductory chapter, we provide brief details of different phospholipases.
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Affiliation(s)
- Ahmed Aloulou
- National School of Engineers of Sfax, University of Sfax, Sfax, Tunisia.
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6
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Lei X, Ahn K, Zhu L, Ubarretxena-Belandia I, Li YM. Soluble oligomers of the intramembrane serine protease YqgP are catalytically active in the absence of detergents. Biochemistry 2008; 47:11920-9. [PMID: 18937501 DOI: 10.1021/bi800385r] [Citation(s) in RCA: 11] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
Abstract
Rhomboid, a polytopic membrane serine protease, represents a unique class of proteases that cleave substrates within the transmembrane domain. Elucidating the mechanism of this extraordinary catalysis comes with inherent challenges related to membrane-associated peptide hydrolysis. Here we established a system that allows expression and isolation of YqgP, a rhomboid homologue from Bacillus subtilis, as a soluble protein. Intriguingly, soluble YqgP is able to specifically cleave a peptide substrate that contains the transmembrane domain of Spitz. Mutation of the catalytic dyad abolished protease activity, and substitution of another highly conserved residue, Asn241, with Ala or Asp significantly reduced the catalytic efficiency of YqgP. We have identified the cleavage site that resides in the middle of the transmembrane domain of Spitz. Replacement of two residues that contribute to the scissile bond by Ala did not eliminate cleavage, but rather led to additional or alternative cleavages. Moreover, we have demonstrated that soluble YqgP exists as oligomers that are required for catalytic activity. These results suggest that soluble oligomers of maltose binding protein-YqgP complexes form micellelike structures that are able to retain the active conformation of the protease for catalysis. Therefore, this work not only provides a unique system for elucidating the reaction mechanism of rhomboid but also will facilitate the characterization of other intramembrane proteases as well as non-protease membrane proteins.
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Affiliation(s)
- Xiaojun Lei
- Molecular Pharmacology and Chemistry Program, Memorial Sloan Kettering Cancer Center, New York, New York 10021, USA.
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7
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Bishop RE. Structural biology of membrane-intrinsic beta-barrel enzymes: sentinels of the bacterial outer membrane. BIOCHIMICA ET BIOPHYSICA ACTA 2008; 1778:1881-96. [PMID: 17880914 PMCID: PMC5007122 DOI: 10.1016/j.bbamem.2007.07.021] [Citation(s) in RCA: 105] [Impact Index Per Article: 6.6] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 05/25/2007] [Revised: 06/28/2007] [Accepted: 07/24/2007] [Indexed: 02/06/2023]
Abstract
The outer membranes of Gram-negative bacteria are replete with integral membrane proteins that exhibit antiparallel beta-barrel structures, but very few of these proteins function as enzymes. In Escherichia coli, only three beta-barrel enzymes are known to exist in the outer membrane; these are the phospholipase OMPLA, the protease OmpT, and the phospholipidColon, two colonslipid A palmitoyltransferase PagP, all of which have been characterized at the structural level. Structural details have also emerged for the outer membrane beta-barrel enzyme PagL, a lipid A 3-O-deacylase from Pseudomonas aeruginosa. Lipid A can be further modified in the outer membrane by two beta-barrel enzymes of unknown structure; namely, the Salmonella enterica 3'-acyloxyacyl hydrolase LpxR, and the Rhizobium leguminosarum oxidase LpxQ, which employs O(2) to convert the proximal glucosamine unit of lipid A into 2-aminogluconate. Structural biology now indicates how beta-barrel enzymes can function as sentinels that remain dormant when the outer membrane permeability barrier is intact. Host immune defenses and antibiotics that perturb this barrier can directly trigger beta-barrel enzymes in the outer membrane. The ensuing adaptive responses occur instantaneously and rapidly outpace other signal transduction mechanisms that similarly function to restore the outer membrane permeability barrier.
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Affiliation(s)
- Russell E Bishop
- Department of Biochemistry and Biomedical Sciences, 1200 Main Street West, Health Sciences Centre 4H19, McMaster University, Hamilton, ON, Canada L8N 3Z5.
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8
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Istivan TS, Smith SC, Fry BN, Coloe PJ. Characterization of Campylobacter concisus hemolysins. ACTA ACUST UNITED AC 2008; 54:224-35. [PMID: 18754784 DOI: 10.1111/j.1574-695x.2008.00467.x] [Citation(s) in RCA: 22] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/13/2022]
Abstract
Campylobacter concisus is an opportunistic pathogen commonly found in the human oral cavity. It has also been isolated from clinical sources including gastroenteritis cases. Both secreted and cell-associated hemolytic activities were detected in C. concisus strains isolated from children with gastroenteritis. The secreted hemolytic activity of C. concisus strains was labile and was detected in variable levels from fresh-culture filtrates only. In addition, another secreted hemolysin/cytotoxin with a molecular weight < 10 kDa was detected in a single C. concisus strain (RCH 12). A C. concisus genomic library, constructed from strain RCH 3 in Escherichia coli XL1-Blue, was screened for hemolytic clones. Subcloning and sequence analysis of selected hemolytic clones identified ORFs for genes that enhance hemolytic activity but do not appear to be related to any known hemolysin genes found in Gram-negative bacteria. In a previous study, a stable cell-associated hemolysin was identified as an outer-membrane phospholipase A (OMPLA) encoded by the pldA gene. In this study, we report cloning of the pldA gene of the clinical strain C. concisus RCH 3 and the complementation of phospholipase A activity in an E. coli pldA mutant.
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9
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Istivan TS, Coloe PJ. Phospholipase A in Gram-negative bacteria and its role in pathogenesis. MICROBIOLOGY-SGM 2006; 152:1263-1274. [PMID: 16622044 DOI: 10.1099/mic.0.28609-0] [Citation(s) in RCA: 101] [Impact Index Per Article: 5.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 11/18/2022]
Abstract
Phospholipase A (PLA) is one of the few enzymes present in the outer membrane of Gram-negative bacteria, and is likely to be involved in the membrane disruption processes that occur during host cell invasion. Both secreted and membrane-bound phospholipase A(2) activities have been described in bacteria, fungi and protozoa. Recently there have been increasing reports on the involvement of PLA in bacterial invasion and pathogenesis. This review highlights the latest findings on PLA as a virulence factor in Gram-negative bacteria.
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Affiliation(s)
- Taghrid S Istivan
- Biotechnology and Environmental Biology, School of Applied Sciences, RMIT University, Bundoora West Campus, PO Box 71, Bundoora, Melbourne, VIC 3083, Australia
| | - Peter J Coloe
- Biotechnology and Environmental Biology, School of Applied Sciences, RMIT University, Bundoora West Campus, PO Box 71, Bundoora, Melbourne, VIC 3083, Australia
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10
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Kim DSH, Chao Y, Saier MH. Protein-translocating trimeric autotransporters of gram-negative bacteria. J Bacteriol 2006; 188:5655-67. [PMID: 16885434 PMCID: PMC1540064 DOI: 10.1128/jb.01596-05] [Citation(s) in RCA: 21] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022] Open
Affiliation(s)
- David S H Kim
- Department of Biological Sciences, University of California at San Diego, 9500 Gilman Dr., La Jolla, CA 92093-0116, USA
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11
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Rutten L, Geurtsen J, Lambert W, Smolenaers JJM, Bonvin AM, de Haan A, van der Ley P, Egmond MR, Gros P, Tommassen J. Crystal structure and catalytic mechanism of the LPS 3-O-deacylase PagL from Pseudomonas aeruginosa. Proc Natl Acad Sci U S A 2006; 103:7071-6. [PMID: 16632613 PMCID: PMC1564273 DOI: 10.1073/pnas.0509392103] [Citation(s) in RCA: 56] [Impact Index Per Article: 3.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/18/2022] Open
Abstract
Pathogenic gram-negative bacteria can modify the lipid A portion of their lipopolysaccharide in response to environmental stimuli. 3-O-deacylation of lipid A by the outer membrane enzyme PagL modulates signaling through Toll-like receptor 4, leading to a reduced host immune response. We found that PagL is widely disseminated among gram-negative bacteria. Only four residues are conserved: a Ser, His, Phe, and Asn residue. Here, we describe the crystal structure of PagL from Pseudomonas aeruginosa to 2.0-A resolution. It consists of an eight-stranded beta-barrel with the axis tilted by approximately 30 degrees with respect to the lipid bilayer. The structure reveals that PagL contains an active site with a Ser-His-Glu catalytic triad and an oxyanion hole that comprises the conserved Asn. The importance of active site residues was confirmed in mutagenesis studies. Although PagL is most likely active as a monomer, its active site architecture shows high resemblance to that of the dimeric 12-stranded outer membrane phospholipase A. Modeling of the substrate lipid X onto the active site reveals that the 3-O-acyl chain is accommodated in a hydrophobic groove perpendicular to the membrane plane. In addition, an aspartate makes a hydrogen bond with the hydroxyl group of the 3-O-acyl chain, probably providing specificity of PagL toward lipid A.
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Affiliation(s)
- Lucy Rutten
- Departments of *Crystal and Structural Chemistry
| | - Jeroen Geurtsen
- Department of Molecular Microbiology, Utrecht University, Padualaan 8, 3584 CH, Utrecht, The Netherlands; and
- Netherlands Vaccine Institute, P.O. Box 457, 3720 AL, Bilthoven, The Netherlands
| | | | | | | | - Alex de Haan
- Netherlands Vaccine Institute, P.O. Box 457, 3720 AL, Bilthoven, The Netherlands
| | - Peter van der Ley
- Netherlands Vaccine Institute, P.O. Box 457, 3720 AL, Bilthoven, The Netherlands
| | | | - Piet Gros
- Departments of *Crystal and Structural Chemistry
| | - Jan Tommassen
- Department of Molecular Microbiology, Utrecht University, Padualaan 8, 3584 CH, Utrecht, The Netherlands; and
- **To whom correspondence should be addressed. E-mail:
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12
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Baaden M, Meier C, Sansom MSP. A molecular dynamics investigation of mono and dimeric states of the outer membrane enzyme OMPLA. J Mol Biol 2003; 331:177-89. [PMID: 12875844 DOI: 10.1016/s0022-2836(03)00718-6] [Citation(s) in RCA: 33] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/19/2022]
Abstract
OMPLA is a phospholipase found in the outer membranes of many Gram-negative bacteria. Enzyme activation requires calcium-induced dimerisation plus bilayer perturbation. As the conformation of OMPLA in the different crystal forms (monomer versus dimer; with/without bound Ca(2+)) is remarkably similar we have used multi-nanosecond molecular dynamics (MD) simulations to probe possible differences in conformational dynamics that may be related to enzyme activation. Simulations of calcium-free monomeric OMPLA, of the Ca(2+)-bound dimer, and of the Ca(2+)-bound dimer with a substrate analogue covalently linked to the active site serine have been performed, all with the protein embedded in a phospholipid (POPC) bilayer. All simulations were stable, but differences in the dynamic behaviour of the protein between the various states were observed. In particular, the stability of the active site and the hydrophobic substrate-binding cleft varied. Dimeric OMPLA is less flexible than monomeric OMPLA, especially around the active site. In the absence of bound substrate analogue, the hydrophobic substrate-binding cleft of dimeric OMPLA collapses. A model is proposed whereby the increased stability of the active site in dimeric OMPLA is a consequence of the local ordering of water around the nearby calcium ion. The observed collapse of the substrate-binding cleft may explain the experimentally observed occurrence of multiple dimer conformations of OMPLA, one of which is fully active while the other shows significantly reduced activity.
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Affiliation(s)
- Marc Baaden
- Department of Biochemistry, University of Oxford, South Parks Road Oxford, OX1 3QU, UK
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13
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Lu H, Tsai SC, Khosla C, Cane DE. Expression, site-directed mutagenesis, and steady state kinetic analysis of the terminal thioesterase domain of the methymycin/picromycin polyketide synthase. Biochemistry 2002; 41:12590-7. [PMID: 12379101 DOI: 10.1021/bi026006d] [Citation(s) in RCA: 52] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/30/2022]
Abstract
The thioesterase (TE) domain of the methymycin/picromycin synthase (PICS) was functionally expressed in Escherichia coli, and the optimal N-terminal boundary of the recombinant TE was determined. A series of diketide-N-acetylcysteamine (SNAC) thioesters were tested as substrates. PICS TE showed a strong preference for the 2-methyl-3-ketopentanoyl-SNAC substrate 5 over the stereoisomers of the reduced diketides 1-4, with an approximately 1.6:1 preference for the (2R,3S)-2-methyl-3-hydroxy diastereomer 2 over the (2S,3R)-diketide 1. The closely related DEBS TE, the thioesterase from the 6-deoxyerythronolide B synthase, showed a more marked 4.4:1 preference for 2 over 1, with only a slightly greater preference for the 3-ketoacyl-SNAC substrate 5. The roles of several active site residues in PICS TE were examined by site-directed mutagenesis. Serine 148, which is part of the apparent catalytic triad consisting of S148, H268, and D176, was found to be essential for thioesterase activity, while replacement of D176 with asparagine (D176N) gave a mutant thioesterase that retained substantial, albeit reduced, hydrolytic activity toward diketide-SNAC substrates. Mutation of E187 and R191, each of which is thought to play a role in substrate binding, had only minor effects on the relative specificity for diketide substrates 1, 2, and 5. Finally, when PICS TE was fused to the C-terminus of DEBS module 3, the resultant chimeric protein converted diketide 1 with methylmalonyl-CoA to triketide ketolactone 6 with improved catalytic efficiency compared to that of the previously developed DEBS module 3-(DEBS)TE construct.
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Affiliation(s)
- Hongxiang Lu
- Department of Chemistry, Brown University, Box H, Providence, Rhode Island 02912-9108, USA
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14
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Kingma RL, Snijder HJ, Dijkstra BW, Dekker N, Egmond MR. Functional importance of calcium binding sites in outer membrane phospholipase A. BIOCHIMICA ET BIOPHYSICA ACTA 2002; 1561:230-7. [PMID: 11997123 DOI: 10.1016/s0005-2736(02)00351-6] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 11/22/2022]
Abstract
Outer membrane phospholipase A (OMPLA) is an integral membrane enzyme that hydrolyses phospholipids requiring Ca(2+) as cofactor. In vitro studies have shown that OMPLA is only active as a dimer. The structures of monomeric and dimeric OMPLA provided possible clues to the activation process. In the inhibited dimeric species calcium ions are located at the dimer interface ideally suited to stabilise the oxyanion intermediates formed during catalysis. The side chain hydroxyl function of Ser152 is one of the ligands of this interfacial calcium. In the crystal structure of monomeric OMPLA the interfacial calcium site is lacking, but calcium was found to bind at a site involving the carboxylates of Asp149 and Asp184. In the current study the relevance of the identified calcium sites has been studied by site-directed mutagenesis. The Ser152Asn variant confirmed the importance of the interfacial calcium site for catalysis, and also demonstrated that this site is essentially involved in the dimerisation process. Replacements of the ligands in monomeric OMPLA, i.e. Asp149Asn, Asp149Ala and Asp184Asn, only showed minor effects on catalytic activity and dimerisation. A stronger effect observed for the variant Asp184Ala was explained by the proximity of Asp184 to the catalytically important Ser152 residue. We propose that Asp149 and Asp184 provide an electronegative funnel that may facilitate Ca(2+) transfer to the interfacial calcium site.
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Affiliation(s)
- Roelie L Kingma
- Department of Membrane Enzymology, Centre for Biomembranes and Lipid Enzymology, Institute of Biomembranes, Utrecht University, P.O. Box 80054, 3508 TB Utrecht, Netherlands
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15
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Abstract
Outer membrane phospholipase A (OMPLA) activity is regulated by reversible dimerisation with the dimer being the active species. Observed lag phases in activity indicated that dimerisation may be slow relative to turnover. A covalent OMPLA dimer indeed did not display lag phase behaviour. A model for OMPLA kinetics was proposed accounting for a slow dimerisation step. Preincubation conditions determined the initial amount of monomer and influenced both lag times and final activities. Under the conditions used, substrate concentrations higher than 50 mol% inhibited OMPLA activity and increased lag times. Our results may shed more light on mechanisms controlling OMPLA activity in vivo.
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Affiliation(s)
- Roelie L Kingma
- Department of Membrane Enzymology, Centre for Biomembranes and Lipid Enzymology, Institute of Biomembranes, Utrecht University, Padualaan 8, 3584 CH, Utrecht, The Netherlands
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16
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Kingma RL, Egmond MR. Activation of a covalent outer membrane phospholipase A dimer. EUROPEAN JOURNAL OF BIOCHEMISTRY 2002; 269:2178-85. [PMID: 11985596 DOI: 10.1046/j.1432-1033.2002.02873.x] [Citation(s) in RCA: 10] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 11/20/2022]
Abstract
The activity of outer membrane phospholipase A (OMPLA) is regulated by reversible dimerization. However, native OMPLA reconstituted in phospholipid vesicles was found to be present as a dimer but nevertheless inactive. To investigate the importance of dimerization for control of OMPLA activity, a covalent OMPLA dimer was constructed and its properties were compared to native OMPLA both in a micellar detergent and after reconstitution in a phospholipid bilayer. Unlike native OMPLA, activity of the covalent OMPLA dimer was independent of type and concentration of detergent in micellar systems. In such systems, the covalent OMPLA dimer invariantly displayed high calcium affinity. In contrast, high calcium concentrations were required to activate a covalent OMPLA dimer when present in intact vesicles. Solubilization of the vesicles increased the affinity for calcium, suggesting that in an intact bilayer the dimer interface is not properly formed. This was supported by the observation that OMPLA variants having an impaired dimeric interface also lacked high affinity calcium binding. A covalent linkage was not able to restore high affinity calcium binding in these variants, demonstrating that a proper dimer interface is essential for optimal catalysis.
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Affiliation(s)
- Roelie L Kingma
- Department of Membrane Enzymology, Centre for Biomembranes and Lipid Enzymology, Institute of Biomembranes, Utrecht University, the Netherlands
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17
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Hoa NT, Brannigan JA, Cutting SM. The Bacillus subtilis signaling protein SpoIVB defines a new family of serine peptidases. J Bacteriol 2002; 184:191-9. [PMID: 11741860 PMCID: PMC134772 DOI: 10.1128/jb.184.1.191-199.2002] [Citation(s) in RCA: 27] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022] Open
Abstract
The protein SpoIVB plays a key role in signaling in the final sigma(K) checkpoint of Bacillus subtilis. This regulatory mechanism coordinates late gene expression during development in this organism and we have recently shown SpoIVB to be a serine peptidase. SpoIVB signals by transiting a membrane, undergoing self-cleavage, and then by an unknown mechanism activating a zinc metalloprotease, SpoIVFB, which cleaves pro-final sigma(K) to its active form, final sigma(K), in the outer mother cell chamber of the developing cell. In this work we have characterized the serine peptidase domain of SpoIVB. Alignment of SpoIVB with homologues from other spore formers has allowed site-specific mutagenesis of all potential active site residues within the peptidase domain. We have defined the putative catalytic domain of the SpoIVB serine peptidase as a 160-amino-acid residue segment at the carboxyl terminus of the protein. His236 and Ser378 are the most important residues for proteolysis, with Asp363 being the most probable third member of the catalytic triad. In addition, we have shown that mutations at residues Asn290 and His394 lead to delayed signaling in the final sigma(K) checkpoint. The active site residues suggest that SpoIVB and its homologues from other spore formers are members of a new family of serine peptidases of the trypsin superfamily.
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Affiliation(s)
- Ngo T Hoa
- School of Biological Sciences, Royal Holloway University of London, Egham, Surrey, TW20 0EX, United Kingdom
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18
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Tannaes T, Dekker N, Bukholm G, Bijlsma JJ, Appelmelk BJ. Phase variation in the Helicobacter pylori phospholipase A gene and its role in acid adaptation. Infect Immun 2001; 69:7334-40. [PMID: 11705905 PMCID: PMC98819 DOI: 10.1128/iai.69.12.7334-7340.2001] [Citation(s) in RCA: 50] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/11/2023] Open
Abstract
Previously, we have shown that Helicobacter pylori can spontaneously and reversibly change its membrane lipid composition, producing variants with low or high content of lysophospholipids. The "lyso" variant contains a high percentage of lysophospholipids, adheres better to epithelial cells, and releases more proteins such as urease and VacA, compared to the "normal" variant, which has a low content of lysophospholipids. Prolonged growth of the normal variant at pH 3.5, but not under neutral conditions, leads to enrichment of lyso variant colonies, suggesting that the colony switch is relevant to acid adaptation. In this study we show that the change in membrane lipid composition is due to phase variation in the pldA gene. A change in the (C) tract length of this gene results in reversible frameshifts, translation of a full-length or truncated pldA, and the production of active or inactive outer membrane phospholipase A (OMPLA). The role of OMPLA in determining the colony morphology was confirmed by the construction of an OMPLA-negative mutant. Furthermore, variants with an active OMPLA were able to survive acidic conditions better than variants with the inactive form. This explains why the lyso variant is selected at low pH. Our studies demonstrate that phase variation in the pldA gene, resulting in an active form of OMPLA, is important for survival under acidic conditions. We also demonstrated the active OMPLA genotype in fresh isolates of H. pylori from patients referred to gastroscopy for dyspepsia.
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Affiliation(s)
- T Tannaes
- Institute of Medical Microbiology, University of Oslo, Oslo, Norway.
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19
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Snijder HJ, Van Eerde JH, Kingma RL, Kalk KH, Dekker N, Egmond MR, Dijkstra BW. Structural investigations of the active-site mutant Asn156Ala of outer membrane phospholipase A: function of the Asn-His interaction in the catalytic triad. Protein Sci 2001; 10:1962-9. [PMID: 11567087 PMCID: PMC2374211 DOI: 10.1110/ps.17701] [Citation(s) in RCA: 13] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/16/2022]
Abstract
Outer membrane phospholipase A (OMPLA) from Escherichia coli is an integral-membrane enzyme with a unique His-Ser-Asn catalytic triad. In serine proteases and serine esterases usually an Asp occurs in the catalytic triad; its role has been the subject of much debate. Here the role of the uncharged asparagine in the active site of OMPLA is investigated by structural characterization of the Asn156Ala mutant. Asparagine 156 is not involved in maintaining the overall active-site configuration and does not contribute significantly to the thermal stability of OMPLA. The active-site histidine retains an active conformation in the mutant notwithstanding the loss of the hydrogen bond to the asparagine side chain. Instead, stabilization of the correct tautomeric form of the histidine can account for the observed decrease in activity of the Asn156Ala mutant.
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Affiliation(s)
- H J Snijder
- Laboratory of Biophysical Chemistry, BIOSON Research Institute, University of Groningen, 9747 AG Groningen, The Netherlands
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20
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Snijder HJ, Kingma RL, Kalk KH, Dekker N, Egmond MR, Dijkstra BW. Structural investigations of calcium binding and its role in activity and activation of outer membrane phospholipase A from Escherichia coli. J Mol Biol 2001; 309:477-89. [PMID: 11371166 DOI: 10.1006/jmbi.2001.4675] [Citation(s) in RCA: 29] [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
Outer membrane phospholipase A (OMPLA) is an integral membrane enzyme that catalyses the hydrolysis of phospholipids. Enzymatic activity is regulated by reversible dimerisation and calcium-binding. We have investigated the role of calcium by X-ray crystallography. In monomeric OMPLA, one calcium ion binds between two external loops (L3L4 site) at 10 A from the active site. After dimerisation, a new calcium-binding site (catalytic site) is formed at the dimer interface in the active site of each molecule at 6 A from the L3L4 calcium site. The close spacing and the difference in calcium affinity of both sites suggests that the L3L4 site may function as a storage site for a calcium ion, which relocates to the catalytic site upon dimerisation. A sequence alignment demonstrates conservation of the catalytic calcium site but evolutionary variation of the L3L4 site. The residues in the dimer interface are conserved as well, suggesting that all outer membrane phospholipases require dimerisation and calcium in the catalytic site for activity. For this family of phospholipases, we have characterised a consensus sequence motif (YTQ-X(n)-G-X(2)-H-X-SNG) that contains conserved residues involved in dimerisation and catalysis.
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Affiliation(s)
- H J Snijder
- Laboratory of Biophysical Chemistry, BIOSON Research Institute, University of Groningen, Nijenborgh 4 9747 AG, Groningen, The Netherlands.
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21
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Jia Y, Yuan W, Wodzinska J, Park C, Sinskey AJ, Stubbe J. Mechanistic studies on class I polyhydroxybutyrate (PHB) synthase from Ralstonia eutropha: class I and III synthases share a similar catalytic mechanism. Biochemistry 2001; 40:1011-9. [PMID: 11170423 DOI: 10.1021/bi002219w] [Citation(s) in RCA: 75] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/17/2022]
Abstract
The Class I and III polyhydroxybutyrate (PHB) synthases from Ralstonia eutropha and Chromatium vinosum, respectively, catalyze the polymerization of beta-hydroxybutyryl-coenzyme A (HBCoA) to generate PHB. These synthases have different molecular weights, subunit composition, and kinetic properties. Recent studies with the C. vinosum synthase suggested that it is structurally homologous to bacterial lipases and allowed identification of active site residues important for catalysis [Jia, Y., Kappock, T. J., Frick, T., Sinskey, A. J., and Stubbe, J. (2000) Biochemistry 39, 3927-3936]. Sequence alignments between the Class I and III synthases revealed similar residues in the R. eutropha synthase. Site-directed mutants of these residues were prepared and examined using HBCoA and a terminally saturated trimer of HBCoA (sT-CoA) as probes. These studies reveal that the R. eutropha synthase possesses an essential catalytic dyad (C319-H508) in which the C319 is involved in covalent catalysis. A conserved Asp, D480, was shown not to be required for acylation of C319 by sT-CoA and is proposed to function as a general base catalyst to activate the hydroxyl of HBCoA for ester formation. Studies of the [(3)H]sT-CoA with wild-type and mutant synthases reveal that 0.5 equiv of radiolabel is covalently bound per monomer of synthase, suggesting that a dimeric form of the enzyme is involved in elongation. These studies, in conjunction with search algorithms for secondary structure, suggest that the Class I and III synthases are mechanistically similar and structurally homologous, despite their physical and kinetic differences.
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Affiliation(s)
- Y Jia
- Department of Chemistry, Massachusetts Institute of Technology, 77 Massachusetts Avenue, Cambridge, Massachusetts 02139, USA
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22
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Snijder HJ, Dijkstra BW. Bacterial phospholipase A: structure and function of an integral membrane phospholipase. BIOCHIMICA ET BIOPHYSICA ACTA 2000; 1488:91-101. [PMID: 11080680 DOI: 10.1016/s1388-1981(00)00113-x] [Citation(s) in RCA: 70] [Impact Index Per Article: 2.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 11/19/2022]
Abstract
Within the large family of lipolytic enzymes, phospholipases constitute a very diverse subgroup with physiological functions such as digestion and signal transduction. Most phospholipases may associate with membranes at the lipid-water interface. However, in many Gram-negative bacteria, a phospholipase is present which is located integrally in the bacterial outer membrane. This phospholipase (outer membrane phospholipase A or OMPLA) is involved in transport across the bacterial outer membrane and has been implicated in bacterial virulence. OMPLA is calcium dependent and its activity is strictly regulated by reversible dimerisation. Recently the crystal structure of this integral membrane enzyme has been elucidated. In this review, we summarise the implications of these structural data for the understanding of the function and regulation of OMPLA, and discuss a mechanism for phospholipase dependent colicin release in Escherichia coli.
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Affiliation(s)
- H J Snijder
- Laboratory of Biophysical Chemistry, BIOSON Research Institute, University of Groningen, Nijenborgh 4, 9747 AG, Groningen, The Netherlands
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