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Biggers L, Elhabashy H, Ackad E, Yousef MS. Molecular dynamics simulations of an engineered T4 lysozyme exclude helix to sheet transition, and provide insights into long distance, intra-protein switchable motion. Protein Sci 2020; 29:542-554. [PMID: 31702853 PMCID: PMC6954740 DOI: 10.1002/pro.3780] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/18/2019] [Revised: 09/23/2019] [Accepted: 11/05/2019] [Indexed: 01/05/2023]
Abstract
An engineered variant of T4 lysozyme serves as a model for studying induced remote conformational changes in a full protein context. The design involves a duplicated surface helix, flanked by two loops, that switches between two different conformations spanning about 20 Å. Molecular dynamics simulations of the engineered protein, up to 1 μs, rule out α-helix to β-sheet transitions within the duplicated helix as suggested by others. These simulations highlight how the use of different force fields can lead to radical differences in the structure of the protein. In addition, Markov state modeling and transition path theory were employed to map a 6.6 μs simulation for possible early intermediate states and to provide insights into the onset of the switching motion. The putative intermediates involve the folding of one helical turn in the C-terminal loop through energy driven, sequential rearrangement of nearby salt bridges around the key residue Arg63. These results provide a first step towards understanding the energetics and dynamics of a rather complicated intra-protein motion.
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Affiliation(s)
- Laurence Biggers
- Department of Internal MedicineUniversity of Texas Southwestern Medical CenterDallasTexas
| | - Hadeer Elhabashy
- Biomolecular Interactions, Max Planck Institute for Developmental BiologyTübingenGermany
| | - Edward Ackad
- Department of PhysicsCollege of Arts and Sciences, Southern Illinois University EdwardsvilleEdwardsvilleIllinois
| | - Mohammad S. Yousef
- Premedical Unit, Weill Cornell Medicine‐QatarCornell UniversityDohaQatar
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2
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Kumar A, Nokhrin S, Woloschuk RM, Woolley GA. Duplication of a Single Strand in a β-Sheet Can Produce a New Switching Function in a Photosensory Protein. Biochemistry 2018; 57:4093-4104. [PMID: 29897240 DOI: 10.1021/acs.biochem.8b00445] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/06/2023]
Abstract
Duplication of a single β-strand that forms part of a β-sheet in photoactive yellow protein (PYP) was found to produce two approximately isoenergetic protein conformations, in which either the first or the second copy of the duplicated β-strand participates in the β-sheet. Whereas one conformation (big-loop) is more stable at equilibrium in the dark, the other conformation (long-tail) is populated after recovery from blue light irradiation. By appending a recognition motif (E-helix) to the C-terminus of the protein, we show that β-strand duplication, and the resulting possibility of β-strand slippage, can lead to a new switchable protein-protein interaction. We suggest that β-strand duplication may be a general means of introducing two-state switching activity into protein structures.
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Affiliation(s)
- Anil Kumar
- Department of Chemistry , University of Toronto , 80 St. George Street , Toronto , ON M5S 3H6 , Canada
| | - Sergiy Nokhrin
- Department of Chemistry , University of Toronto , 80 St. George Street , Toronto , ON M5S 3H6 , Canada
| | - Ryan M Woloschuk
- Department of Chemistry , University of Toronto , 80 St. George Street , Toronto , ON M5S 3H6 , Canada
| | - G Andrew Woolley
- Department of Chemistry , University of Toronto , 80 St. George Street , Toronto , ON M5S 3H6 , Canada
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3
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Bahramali G, Goliaei B, Minuchehr Z, Salari A. Chameleon sequences in neurodegenerative diseases. Biochem Biophys Res Commun 2016; 472:209-16. [PMID: 26920059 PMCID: PMC7124260 DOI: 10.1016/j.bbrc.2016.01.187] [Citation(s) in RCA: 8] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/23/2016] [Accepted: 01/30/2016] [Indexed: 01/03/2023]
Abstract
Chameleon sequences can adopt either alpha helix sheet or a coil conformation. Defining chameleon sequences in PDB (Protein Data Bank) may yield to an insight on defining peptides and proteins responsible in neurodegeneration. In this research, we benefitted from the large PDB and performed a sequence analysis on Chameleons, where we developed an algorithm to extract peptide segments with identical sequences, but different structures. In order to find new chameleon sequences, we extracted a set of 8315 non-redundant protein sequences from the PDB with an identity less than 25%. Our data was classified to "helix to strand (HE)", "helix to coil (HC)" and "strand to coil (CE)" alterations. We also analyzed the occurrence of singlet and doublet amino acids and the solvent accessibility in the chameleon sequences; we then sorted out the proteins with the most number of chameleon sequences and named them Chameleon Flexible Proteins (CFPs) in our dataset. Our data revealed that Gly, Val, Ile, Tyr and Phe, are the major amino acids in Chameleons. We also found that there are proteins such as Insulin Degrading Enzyme IDE and GTP-binding nuclear protein Ran (RAN) with the most number of chameleons (640 and 405 respectively). These proteins have known roles in neurodegenerative diseases. Therefore it can be inferred that other CFP's can serve as key proteins in neurodegeneration, and a study on them can shed light on curing and preventing neurodegenerative diseases.
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Affiliation(s)
- Golnaz Bahramali
- Institute of Biochemistry and Biophysics, University of Tehran, Tehran, Iran
| | - Bahram Goliaei
- Institute of Biochemistry and Biophysics, University of Tehran, Tehran, Iran.
| | - Zarrin Minuchehr
- Department of Systems Biotechnology, National Institute of Genetic Engineering and Biotechnology, (NIGEB), Tehran, Iran.
| | - Ali Salari
- Department of Systems Biotechnology, National Institute of Genetic Engineering and Biotechnology, (NIGEB), Tehran, Iran
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4
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Kaur H, Sasidhar YU. Environmental polarity induces conformational transitions in a helical peptide sequence from bacteriophage T4 lysozyme and its tandem duplicate: a molecular dynamics simulation study. J Mol Model 2015; 21:88. [PMID: 25773700 DOI: 10.1007/s00894-015-2621-5] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/20/2014] [Accepted: 02/15/2015] [Indexed: 11/29/2022]
Abstract
Our recent molecular dynamics (MD) simulation of an insertion/duplication mutant 'L20' of bacteriophage T4 lysozyme demonstrated a solvent induced α→β transition in a loosely held duplicate helical region, while α-helical conformation in the parent region was relatively stabilized by its tertiary interactions with the neighboring residues. The solution NMR of the parent helical sequence, sans its protein context, showed no inherent tendency to adopt a particular secondary structure in pure water but showed α-helical propensity in TFE/water and SDS micelles. In this study we investigate the conformational preference of the 'parent' and 'duplicate' sequences, sans the protein context, in pure water and an apolar TFE/water solution. Apolar TFE/water solution is a model for non-polar protein context. We performed MD simulations of the two peptides, in explicit water and 80% (v/v) TFE/water, using GROMOS 53a6 force field, at 300 K and 1 bar (under NPT conditions). We show that in TFE/water mixture, salt bridges are stabilized by apolar TFE molecules and main chain-main chain hydrogen bonds promote the α-helical conformation, particularly in the duplicate peptide. Solvent exposure, in pure water, resulted in an α→β transition to form a triple stranded β-sheet structure in the 'duplicate' sequence, with a rare psi-loop topology, while a mixture of turn/bend conformations were adopted by the 'parent' sequence. Thus the differences in conformational preference of the parent and duplicate sequence sans protein context, in pure water and TFE/water, implicate the importance of the environment polarity in dictating the peptide conformation. Mechanism of folding of the observed psi-loop in the duplicate sequence gives insights into folding of this rare β-sheet topology.
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Affiliation(s)
- Harpreet Kaur
- Department of Chemistry, Indian Institute of Technology Bombay, Powai, Mumbai, 400076, India
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5
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Kaur H, Sasidhar YU. Molecular dynamics study of an insertion/duplication mutant of bacteriophage T4 lysozyme reveals the nature of α→β transition in full protein context. Phys Chem Chem Phys 2013; 15:7819-30. [PMID: 23598905 DOI: 10.1039/c3cp44327b] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/15/2023]
Abstract
An α→β transition underlies the first step of disease causing amyloidogenesis in many proteins. In view of this, many studies have been carried out using peptide models to characterize these secondary structural transitions. In this paper we show that an insertion/duplication mutant 'L20' of bacteriophage T4 lysozyme (M. Sagermann, W. A. Baase and B. W. Matthews, Proc. Natl. Acad. Sci. U.S.A., 1999, 96, 6078) displays an α→β transition. We performed molecular dynamics (MD) simulation of L20, using the GROMACS package of programs and united atom GROMOS 53a6 force field for a time period of 600 ns at 300 K, in explicit water. Our MD simulation demonstrated that the transition occurs in a duplicated α-helical region inserted tandemly at the N-terminus of the 'parent' helix. We show that a C-terminal β-sheet anchors the parent helix while the loosely held N-terminal loop in the duplicate region is vulnerable to solvent attack and thus undergoes an α→β transition. Main chain-solvent interactions were seen to stabilize the observed β-structure. Thus L20 serves as a good protein model for characterization of α→β transition in a full length protein.
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Affiliation(s)
- Harpreet Kaur
- Department of Chemistry, Indian Institute of Technology Bombay, Powai, Mumbai 400 076, India
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6
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Stratton MM, Loh SN. Converting a protein into a switch for biosensing and functional regulation. Protein Sci 2011; 20:19-29. [PMID: 21064163 DOI: 10.1002/pro.541] [Citation(s) in RCA: 40] [Impact Index Per Article: 3.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/16/2022]
Abstract
Proteins that switch conformations in response to a signaling event (e.g., ligand binding or chemical modification) present a unique solution to the design of reagent-free biosensors as well as molecules whose biological functions are regulated in useful ways. The principal roadblock in the path to develop such molecules is that the majority of natural proteins do not change conformation upon binding their cognate ligands or becoming chemically modified. Herein, we review recent protein engineering efforts to introduce switching properties into binding proteins. By co-opting natural allosteric coupling, joining proteins in creative ways and formulating altogether new switching mechanisms, researchers are learning how to coax conformational changes from proteins that previously had none. These studies are providing some answers to the challenging question: how can one convert a lock-and-key binding protein into a molecular switch?
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Affiliation(s)
- Margaret M Stratton
- Department of Biochemistry and Molecular Biology, State University of New York Upstate Medical University, 750 East Adams Street, Syracuse, New York 13210, USA
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7
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Takano K, Katagiri Y, Mukaiyama A, Chon H, Matsumura H, Koga Y, Kanaya S. Conformational contagion in a protein: structural properties of a chameleon sequence. Proteins 2007; 68:617-25. [PMID: 17510955 DOI: 10.1002/prot.21451] [Citation(s) in RCA: 21] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/07/2022]
Abstract
Certain sequences, known as chameleon sequences, take both alpha- and beta-conformations in natural proteins. We demonstrate that a wild chameleon sequence fused to the C-terminal alpha-helix or beta-sheet in foreign stable proteins from hyperthermophiles forms the same conformation as the host secondary structure. However, no secondary structural formation is observed when the sequence is attached to the outside of the secondary structure. These results indicate that this sequence inherently possesses an ability to make either alpha- or beta-conformation, depending on the sequentially neighboring secondary structure if little other nonlocal interaction occurs. Thus, chameleon sequences take on a satellite state through contagion by the power of a secondary structure. We propose this "conformational contagion" as a new nonlocal determinant factor in protein structure and misfolding related to protein conformational diseases.
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Affiliation(s)
- Kazufumi Takano
- Department of Material and Life Science, Osaka University, Suita, Japan.
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8
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Sagermann M, Baase WA, Matthews BW. Sequential reorganization of beta-sheet topology by insertion of a single strand. Protein Sci 2006; 15:1085-92. [PMID: 16597830 PMCID: PMC2242519 DOI: 10.1110/ps.052018006] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/24/2022]
Abstract
Insertions, duplications, and deletions of sequence segments are thought to be major evolutionary mechanisms that increase the structural and functional diversity of proteins. Alternative splicing, for example, is an intracellular editing mechanism that is thought to generate isoforms for 30%-50% of all human genes. Whereas the inserted sequences usually display only minor structural rearrangements at the insertion site, recent observations indicate that they may also cause more dramatic structural displacements of adjacent structures. In the present study we test how artificially inserted sequences change the structure of the beta-sheet region in T4 lysozyme. Copies of two different beta-strands were inserted into two different loops of the beta-sheet, and the structures were determined. Not surprisingly, one insert "loops out" at its insertion site and forms a new small beta-hairpin structure. Unexpectedly, however, the second insertion leads to displacement of adjacent strands and a sequential reorganization of the beta-sheet topology. Even though the insertions were performed at two different sites, looping out occurred at the C-terminal end of the same beta-strand. Reasons as to why a non-native sequence would be recruited to replace that which occurs in the native protein are discussed. Our results illustrate how sequence insertions can facilitate protein evolution through both local and nonlocal changes in structure.
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Affiliation(s)
- Martin Sagermann
- Institute of Molecular Biology, Howard Hughes Medical Institute, and Department of Physics, University of Oregon, Eugene, Oregon 97403-1229, USA
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9
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Iturbe-Ormaetxe I, Burke GR, Riegler M, O'Neill SL. Distribution, expression, and motif variability of ankyrin domain genes in Wolbachia pipientis. J Bacteriol 2005; 187:5136-45. [PMID: 16030207 PMCID: PMC1196006 DOI: 10.1128/jb.187.15.5136-5145.2005] [Citation(s) in RCA: 105] [Impact Index Per Article: 5.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022] Open
Abstract
The endosymbiotic bacterium Wolbachia pipientis infects a wide range of arthropods, in which it induces a variety of reproductive phenotypes, including cytoplasmic incompatibility (CI), parthenogenesis, male killing, and reversal of genetic sex determination. The recent sequencing and annotation of the first Wolbachia genome revealed an unusually high number of genes encoding ankyrin domain (ANK) repeats. These ANK genes are likely to be important in mediating the Wolbachia-host interaction. In this work we determined the distribution and expression of the different ANK genes found in the sequenced Wolbachia wMel genome in nine Wolbachia strains that induce different phenotypic effects in their hosts. A comparison of the ANK genes of wMel and the non-CI-inducing wAu Wolbachia strain revealed significant differences between the strains. This was reflected in sequence variability in shared genes that could result in alterations in the encoded proteins, such as motif deletions, amino acid insertions, and in some cases disruptions due to insertion of transposable elements and premature stops. In addition, one wMel ANK gene, which is part of an operon, was absent in the wAu genome. These variations are likely to affect the affinity, function, and cellular location of the predicted proteins encoded by these genes.
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Affiliation(s)
- Iñaki Iturbe-Ormaetxe
- School of Integrative Biology, The University of Queensland, St. Lucia, QLD 4072, Brisbane, Australia
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10
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Tripp KW, Barrick D. The tolerance of a modular protein to duplication and deletion of internal repeats. J Mol Biol 2004; 344:169-78. [PMID: 15504409 DOI: 10.1016/j.jmb.2004.09.038] [Citation(s) in RCA: 39] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/23/2004] [Revised: 09/16/2004] [Accepted: 09/17/2004] [Indexed: 11/22/2022]
Abstract
Ankyrin repeat polypeptides contain repeated structural elements that pack to produce modular architectures lacking in close contacts between distant segments of the polypeptide chain. Despite this lack of sequence-distant contacts, ankyrin repeat polypeptides have been shown to fold in a cooperative manner. To determine the distance over which cooperative interactions can be propagated in a repeat protein, and to investigate the tolerance to internal duplication and deletion of modules, we have constructed a series of ankyrin repeat variants of the Notch ankyrin domain in which repeat number is varied by duplication and deletion of internal repeats. A construct with two copies of the fifth ankyrin repeat shows a modest increase in stability compared to the parent construct and retains apparent two-state unfolding behavior. Although constructs containing three and four copies of the fifth repeat retain this increased resistance to urea, they exhibit broad, multi-state unfolding transitions compared to the parent construct. For the Notch ankyrin domain, these larger constructs may represent a limit beyond which full cooperativity cannot be maintained. Deletions of internal repeats from the Notch ankyrin domain significantly destabilize the domain. This severe destabilization, which is larger than that resulting from end-repeat deletion, may arise from unfavorable interactions within the new non-native interfaces produced by internal repeat deletion. These results demonstrate both an asymmetry between the duplication and deletion of internal repeats, and a difference between deletion of internal and end-repeats, suggesting preferred mechanisms for evolution of repeat proteins.
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Affiliation(s)
- Katherine W Tripp
- T.C. Jenkins Department of Biophysics, Johns Hopkins University, 3400 North Charles Street, Baltimore, MD 21211, USA
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11
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He MM, Wood ZA, Baase WA, Xiao H, Matthews BW. Alanine-scanning mutagenesis of the beta-sheet region of phage T4 lysozyme suggests that tertiary context has a dominant effect on beta-sheet formation. Protein Sci 2004; 13:2716-24. [PMID: 15340171 PMCID: PMC2286564 DOI: 10.1110/ps.04875504] [Citation(s) in RCA: 14] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/26/2022]
Abstract
In general, alpha-helical conformations in proteins depend in large part on the amino acid residues within the helix and their proximal interactions. For example, an alanine residue has a high propensity to adopt an alpha-helical conformation, whereas that of a glycine residue is low. The sequence preferences for beta-sheet formation are less obvious. To identify the factors that influence beta-sheet conformation, a series of scanning polyalanine mutations were made within the strands and associated turns of the beta-sheet region in T4 lysozyme. For each construct the stability of the folded protein was reduced substantially, consistent with removal of native packing interactions. However, the crystal structures showed that each of the mutants retained the beta-sheet conformation. These results suggest that the structure of the beta-sheet region of T4 lysozyme is maintained to a substantial extent by tertiary interactions with the surrounding parts of the protein. Such tertiary interactions may be important in determining the structures of beta-sheets in general.
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Affiliation(s)
- Molly M He
- Institute of Molecular Biology, Howard Hughes Medical Institute and Department of Physics, 1229 University of Oregon, Eugene, OR 97403-1229, USA
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12
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Yousef MS, Baase WA, Matthews BW. Use of sequence duplication to engineer a ligand-triggered, long-distance molecular switch in T4 lysozyme. Proc Natl Acad Sci U S A 2004; 101:11583-6. [PMID: 15286283 PMCID: PMC511024 DOI: 10.1073/pnas.0404482101] [Citation(s) in RCA: 19] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/18/2022] Open
Abstract
We have designed a molecular switch in a T4 lysozyme construct that controls a large-scale translation of a duplicated helix. As shown by crystal structures of the construct with the switch on and off, the conformational change is triggered by the binding of a ligand (guanidinium ion) to a site that in the wild-type protein was occupied by the guanidino head group of an Arg. In the design template, a duplicated helix is flanked by two loop regions of different stabilities. In the "on" state, the N-terminal loop is weakly structured, whereas the C-terminal loop has a well defined conformation that is stabilized by means of nonbonded interactions with the Arg head group. The truncation of the Arg to Ala destabilizes this loop and switches the protein to the "off" state, in which the duplicated helix is translocated approximately 20 A. Guanidinium binding restores the key interactions, restabilizes the C-terminal loop, and restores the "on" state. Thus, the presence of an external ligand, which is unrelated to the catalytic activity of the enzyme, triggers the inserted helix to translate 20 A away from the binding site. The results illustrate a proposed mechanism for protein evolution in which sequence duplication followed by point mutation can lead to the establishment of new function.
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Affiliation(s)
- Mohammad S Yousef
- Institute of Molecular Biology, Howard Hughes Medical Institute, and Department of Physics, University of Oregon, Eugene, OR 97403-1229, USA.
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13
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Sagermann M, Gay L, Matthews BW. Long-distance conformational changes in a protein engineered by modulated sequence duplication. Proc Natl Acad Sci U S A 2003; 100:9191-5. [PMID: 12869697 PMCID: PMC170894 DOI: 10.1073/pnas.1633549100] [Citation(s) in RCA: 14] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/18/2022] Open
Abstract
There are few, if any, known instances in which a biological signal is transmitted via a large conformational change through the body of a protein. We describe here a mutant of T4 lysozyme that was engineered to permit structural change at a distance. The design uses a tandem sequence repeat that makes it possible to transmit large-scale structural changes from one end of an alpha-helix to the other over a distance of 17-25 A. The method should be of general applicability and may make it possible to introduce a mutation at one site in a protein that will induce large-scale changes in the structure at a spatially remote site.
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Affiliation(s)
- Martin Sagermann
- Institute of Molecular Biology, Howard Hughes Medical Institute and Department of Physics, University of Oregon, Eugene, OR 97403-1229, USA
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14
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Miller ES, Kutter E, Mosig G, Arisaka F, Kunisawa T, Rüger W. Bacteriophage T4 genome. Microbiol Mol Biol Rev 2003; 67:86-156, table of contents. [PMID: 12626685 PMCID: PMC150520 DOI: 10.1128/mmbr.67.1.86-156.2003] [Citation(s) in RCA: 554] [Impact Index Per Article: 26.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022] Open
Abstract
Phage T4 has provided countless contributions to the paradigms of genetics and biochemistry. Its complete genome sequence of 168,903 bp encodes about 300 gene products. T4 biology and its genomic sequence provide the best-understood model for modern functional genomics and proteomics. Variations on gene expression, including overlapping genes, internal translation initiation, spliced genes, translational bypassing, and RNA processing, alert us to the caveats of purely computational methods. The T4 transcriptional pattern reflects its dependence on the host RNA polymerase and the use of phage-encoded proteins that sequentially modify RNA polymerase; transcriptional activator proteins, a phage sigma factor, anti-sigma, and sigma decoy proteins also act to specify early, middle, and late promoter recognition. Posttranscriptional controls by T4 provide excellent systems for the study of RNA-dependent processes, particularly at the structural level. The redundancy of DNA replication and recombination systems of T4 reveals how phage and other genomes are stably replicated and repaired in different environments, providing insight into genome evolution and adaptations to new hosts and growth environments. Moreover, genomic sequence analysis has provided new insights into tail fiber variation, lysis, gene duplications, and membrane localization of proteins, while high-resolution structural determination of the "cell-puncturing device," combined with the three-dimensional image reconstruction of the baseplate, has revealed the mechanism of penetration during infection. Despite these advances, nearly 130 potential T4 genes remain uncharacterized. Current phage-sequencing initiatives are now revealing the similarities and differences among members of the T4 family, including those that infect bacteria other than Escherichia coli. T4 functional genomics will aid in the interpretation of these newly sequenced T4-related genomes and in broadening our understanding of the complex evolution and ecology of phages-the most abundant and among the most ancient biological entities on Earth.
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Affiliation(s)
- Eric S Miller
- Department of Microbiology, North Carolina State University, Raleigh, North Carolina 27695-7615, USA.
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15
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Sagermann M, Matthews BW. Crystal structures of a T4-lysozyme duplication-extension mutant demonstrate that the highly conserved beta-sheet region has low intrinsic folding propensity. J Mol Biol 2002; 316:931-40. [PMID: 11884133 DOI: 10.1006/jmbi.2001.5376] [Citation(s) in RCA: 18] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022]
Abstract
Residues 24 to 35 of T4 lysozyme correspond to the second and third strands of a region of beta-sheet that is highly conserved in all known lysozyme and chitinase structures. To evaluate the intrinsic propensity of these amino acid residues to form a defined structure they were added at the C terminus of the native protein, together with a dipeptide linker. Two crystal structures of this active, mutant protein were obtained, to 1.9A and 2.3A resolution, respectively. Even though the crystal conditions are similar, the appended sequence adopts very different secondary structures. In one case it is weakly structured and appears to extend through the active-site cleft, perhaps in part adding an extra strand to the original beta-sheet. In the other crystal form the extension is largely alpha-helical. The formation of these alternative structures shows that the sequence does not have a strong intrinsic propensity to form a unique fold (either beta-sheet or otherwise). The results also suggest that structural conservation during evolution does not necessarily depend on sequence conservation or the conservation of folding propensity.
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Affiliation(s)
- Martin Sagermann
- Institute of Molecular Biology, Howard Hughes Medical Institute and Department of Physics, 1229 University of Oregon, Eugene, OR 97403-1229, USA
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16
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Nguyen DM, Gittis AG, Lattman EE. The duplication of an eight-residue helical stretch in Staphylococcal nuclease is not helical: a model for evolutionary change. Proteins 2000; 40:465-72. [PMID: 10861938 DOI: 10.1002/1097-0134(20000815)40:3<465::aid-prot130>3.0.co;2-a] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/08/2022]
Abstract
A common method of evolutionary change is gene duplication, followed by other events that lead to new function, decoration of folds, oligomerization, or other changes. As part of a study on the potential for evolutionary change created by duplicated sequences, we have carried out a crystallographic study on a mutant of Staphylococcal nuclease in which residues 55-62 have been duplicated in a wild-type variant termed PHS. In the parental protein (PHS) these residues form the first two turns of a helix running from residue 54 to 68 (hereafter designated as helix I). The crystal structure of the mutant is very similar to that of the parental, with helix I being unaltered. The duplicated residues are accommodated by expanding an existing loop N-terminal to helix I. In addition, circular dichroism (CD) studies have been carried out on a parental peptide containing helix I with six flanking residues at each terminus (residues 48-74) and on the same peptide expanded by the duplication, as a function of 2,2,2-trifluoroethanol (TFE) concentration. Each peptide possesses only modest helical propensity in solution. Our data, which is different from what was observed in T4 lysozyme, show that the conformation of the duplicated sequence is determined by a balance of sequential and longer-range effects. Thus duplicating sequence need not mean duplicating structure. Proteins 2000;40:465-472.
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Affiliation(s)
- D M Nguyen
- Thomas C. Jenkins Department of Biophysics, Johns Hopkins University, Baltimore, Maryland 21218-2685, USA
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17
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Paper Alert. Structure 1999. [DOI: 10.1016/s0969-2126(99)80183-x] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/17/2022]
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