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O'Rourke KF, Axe JM, D'Amico RN, Sahu D, Boehr DD. Millisecond Timescale Motions Connect Amino Acid Interaction Networks in Alpha Tryptophan Synthase. Front Mol Biosci 2018; 5:92. [PMID: 30467546 PMCID: PMC6236060 DOI: 10.3389/fmolb.2018.00092] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/25/2018] [Accepted: 10/18/2018] [Indexed: 11/13/2022] Open
Abstract
Tryptophan synthase is a model system for understanding allosteric regulation within enzyme complexes. Amino acid interaction networks were previously delineated in the isolated alpha subunit (αTS) in the absence of the beta subunit (βTS). The amino acid interaction networks were different between the ligand-free enzyme and the enzyme actively catalyzing turnover. Previous X-ray crystallography studies indicated only minor localized changes when ligands bind αTS, and so, structural changes alone could not explain the changes to the amino acid interaction networks. We hypothesized that the network changes could instead be related to changes in conformational dynamics. As such, we conducted nuclear magnetic resonance relaxation studies on different substrate- and products-bound complexes of αTS. Specifically, we collected 15N R2 relaxation dispersion data that reports on microsecond-to-millisecond timescale motion of backbone amide groups. These experiments indicated that there are conformational exchange events throughout αTS. Substrate and product binding change specific motional pathways throughout the enzyme, and these pathways connect the previously identified network residues. These pathways reach the αTS/βTS binding interface, suggesting that the identified dynamic networks may also be important for communication with the βTS subunit.
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Affiliation(s)
- Kathleen F O'Rourke
- Department of Chemistry, The Pennsylvania State University, University Park, PA, United States
| | - Jennifer M Axe
- Department of Chemistry, The Pennsylvania State University, University Park, PA, United States
| | - Rebecca N D'Amico
- Department of Chemistry, The Pennsylvania State University, University Park, PA, United States
| | - Debashish Sahu
- Department of Chemistry, The Pennsylvania State University, University Park, PA, United States
| | - David D Boehr
- Department of Chemistry, The Pennsylvania State University, University Park, PA, United States
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Zhang W, Guo H, Cao C, Li L, Kwok LY, Zhang H, Sun Z. Adaptation of Lactobacillus casei Zhang to Gentamycin Involves an Alkaline Shock Protein. Front Microbiol 2017; 8:2316. [PMID: 29218040 PMCID: PMC5703869 DOI: 10.3389/fmicb.2017.02316] [Citation(s) in RCA: 10] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/01/2017] [Accepted: 11/09/2017] [Indexed: 12/26/2022] Open
Abstract
Lactobacillus (L. casei) Zhang is a koumiss-originated probiotic strain, which was used as a model in a long-term antibiotics-driven evolution experiment to reveal bacterial evolutionary dynamics; and we isolated gentamycin-resistant L. casei Zhang descendents. To decipher the gentamycin resistance mechanism, here we cultivated the parental L. casei Zhang and its descendent cells in an antibiotics-containing environment to compare their global protein expression profiles using the iTRAQ-based proteomic approach. A total of 72 proteins were significantly up-regulated (>2.0-fold, P < 0.05), whilst 32 proteins were significantly down-regulated <−2.0-fold, P < 0.05) in the descendent line. The gentamycin-resistant descendent line showed elevated expression in some carbohydrates, amino acids, and purine metabolic pathways. Several stress-related proteins were also differentially expressed. Among them, one alkaline shock protein, asp23, was up-regulated most in the gentamycin-resistant strain (21.9-fold increase compared with the parental strain). The asp23 gene disruption mutant was significantly more sensitive to gentamycin compared with the wild type, suggesting an important role of this gene in developing the gentamycin-resistant phenotype in L. casei. Our report has described the adaptation of a probiotic strain that has acquired antibiotics resistance through long-term antibiotics exposure at the proteome level, and we revealed a novel mechanism of gentamycin resistance.
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Affiliation(s)
- Wenyi Zhang
- Key Laboratory of Dairy Biotechnology and Engineering, Ministry of Education, Key Laboratory of Dairy Products Processing, Ministry of Agriculture, Inner Mongolia Agricultural University, Hohhot, China
| | - Huiling Guo
- Key Laboratory of Dairy Biotechnology and Engineering, Ministry of Education, Key Laboratory of Dairy Products Processing, Ministry of Agriculture, Inner Mongolia Agricultural University, Hohhot, China
| | - Chenxia Cao
- Key Laboratory of Dairy Biotechnology and Engineering, Ministry of Education, Key Laboratory of Dairy Products Processing, Ministry of Agriculture, Inner Mongolia Agricultural University, Hohhot, China
| | - Lina Li
- Key Laboratory of Dairy Biotechnology and Engineering, Ministry of Education, Key Laboratory of Dairy Products Processing, Ministry of Agriculture, Inner Mongolia Agricultural University, Hohhot, China
| | - Lai-Yu Kwok
- Key Laboratory of Dairy Biotechnology and Engineering, Ministry of Education, Key Laboratory of Dairy Products Processing, Ministry of Agriculture, Inner Mongolia Agricultural University, Hohhot, China
| | - Heping Zhang
- Key Laboratory of Dairy Biotechnology and Engineering, Ministry of Education, Key Laboratory of Dairy Products Processing, Ministry of Agriculture, Inner Mongolia Agricultural University, Hohhot, China
| | - Zhihong Sun
- Key Laboratory of Dairy Biotechnology and Engineering, Ministry of Education, Key Laboratory of Dairy Products Processing, Ministry of Agriculture, Inner Mongolia Agricultural University, Hohhot, China
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Evran S, Telefoncu A, Sterner R. Directed evolution of ( )8-barrel enzymes: establishing phosphoribosylanthranilate isomerisation activity on the scaffold of the tryptophan synthase -subunit. Protein Eng Des Sel 2012; 25:285-93. [DOI: 10.1093/protein/gzs015] [Citation(s) in RCA: 14] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/30/2022] Open
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Eisenlohr LC, Huang L, Golovina TN. Rethinking peptide supply to MHC class I molecules. Nat Rev Immunol 2007; 7:403-10. [PMID: 17457346 DOI: 10.1038/nri2077] [Citation(s) in RCA: 33] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/08/2022]
Abstract
The notion that peptides bound to MHC class I molecules are derived mainly from newly synthesized proteins that are defective, and are therefore targeted for immediate degradation, has gained wide acceptance. This model, still entirely hypothetical, has strong intuitive appeal and is consistent with some experimental results, but it is strained by other findings, as well as by established and emerging concepts in protein quality control. While not discounting defectiveness as a driving force for the processing of some proteins, we propose that MHC-class-I-restricted epitopes are derived mainly from nascent proteins that are accessed by the degradation machinery prior to any assessment of fitness, and we outline one way in which this could be accomplished.
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Affiliation(s)
- Laurence C Eisenlohr
- Laurence C. Eisenlohr, Lan Huang and Tania N. Golovina are at the Thomas Jefferson University, Jefferson Medical College, Department of Microbiology and Immunology, Philadelphia, Philadelphia 19107, USA
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Jeong MS, Jeong JK, Lim WK, Jang SB. Structures of wild-type and P28L/Y173F tryptophan synthase alpha-subunits from Escherichia coli. Biochem Biophys Res Commun 2004; 323:1257-64. [PMID: 15451433 DOI: 10.1016/j.bbrc.2004.08.222] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/10/2004] [Indexed: 11/24/2022]
Abstract
The alpha-subunit of tryptophan synthase (alphaTS) catalyzes the cleavage of indole-3-glycerol phosphate to glyceraldehyde-3-phosphate and indole, which is used to yield the amino acid tryptophan in tryptophan biosynthesis. Here, we report the first crystal structures of wild-type and double-mutant P28L/Y173F alpha-subunit of tryptophan synthase from Escherichia coli at 2.8 and 1.8A resolution, respectively. The structure of wild-type alphaTS from E. coli was similar to that of the alpha(2)beta(2) complex structure from Salmonella typhimurium. As compared with both structures, the conformational changes are mostly in the interface of alpha- and beta-subunits, and the substrate binding region. Two sulfate ions and two glycerol molecules per asymmetric unit bind with the residues in the active sites of the wild-type structure. Contrarily, double-mutant P28L/Y173F structure is highly closed at the window for the substrate binding by the conformational changes. The P28L substitution induces the exposure of hydrophobic amino acids and decreases the secondary structure that causes the aggregation. The Y173F suppresses to transfer a signal from the alpha-subunit core to the alpha-subunit surface involved in interactions with the beta-subunit and increases structural stability.
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Affiliation(s)
- Mi Suk Jeong
- Korea Nanobiotechnology Center, Pusan National University, Jangjeon-dong, Geumjeong-gu, Busan 609-735, Republic of Korea
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Jeong JK, Shin HJ, Kim JW, Lee CH, Kim HD, Lim WK. Fluorescence and folding properties of Tyr mutant tryptophan synthase alpha-subunits from Escherichia coli. Biochem Biophys Res Commun 2003; 300:29-35. [PMID: 12480516 DOI: 10.1016/s0006-291x(02)02769-9] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/27/2022]
Abstract
The fluorescence of tyrosine has been used to monitor a folding process of tryptophan synthase alpha-subunit from Escherichia coli, because this protein has 7 tyrosines, but not tryptophan. Here to assess the contribution of each Tyr to fluorescence properties of this protein during folding, mutant proteins in which Tyr was replaced with Phe were analyzed. The result shows that a change of Tyr fluorescence occurring during folding of this protein is contributed to approximately 40% each by Tyr(4) and Tyr(115), and to the remaining approximately 20% by Tyr(173) and Tyr(175). Y173F and Y175F mutant proteins showed an increase in their fluorescence intensity by approximately 40% and approximately 10%, respectively. These increases appear to be due to multiple effects of increased hydrophobicity, quenching effect of nearby residue Glu(49), and/or energy transfer between Tyrs. Two data for Y173F alpha-subunit of urea-induced unfolding equilibrium monitored by UV and fluorescence were different. This result, together with ANS binding and far UV CD, shows that folding intermediate(s) of Y173F alpha-subunit, contrary to that of wild-type, may contain self-inconsistent properties such as more buried hydrophobicity, highly quenched fluorescence, and different dependencies on urea of UV absorbance, suggesting an ensemble of heterogeneous structures.
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Affiliation(s)
- Jae Kap Jeong
- Department of Molecular Biology, College of Natural Sciences, Pusan National University, Jangjeon-dong, Keumjeong-district, 609-735, Busan, Republic of Korea
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Kim JW, Kim EY, Park HH, Jung JE, Kim HD, Shin HJ, Lim WK. Homodimers of mutant tryptophan synthase alpha-subunits in Escherichia coli. Biochem Biophys Res Commun 2001; 289:568-72. [PMID: 11716512 DOI: 10.1006/bbrc.2001.6022] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022]
Abstract
Tryptophan synthase alpha-subunit from Escherichia coli functionally exists as a heterotetramer of alpha(2)beta(2) with beta-subunit. While wild-type and mutant (F139W, T24M/F139W, and T24L/F139W) alpha-subunits were expressed as a monomer from recombinant plasmids in Escherichia coli, T24A/F139W, T24S/F139W, and T24K/F139W mutant alpha-subunits were abnormally expressed as soluble homodimers in addition to monomers. Monomers of dimer-forming mutant alpha-subunits retain high affinity to beta-subunit, high activity in stimulating catalytic activities of beta-subunit, and nearly intact content of secondary structure, indicating that the global structures of these monomers are identical to that of F139W alpha-subunit. However, fluorescence spectra of Trp139 and ANS binding indicate that significant perturbations occur in the mutant proteins. Interestingly, these defective properties of monomers caused by residue replacement were partially repaired by the dimer formation. As a result, it is suggested that dimers may be formed by domain or loop swapping, and that residue 24 may play important role in maintaining on-pathway of alpha-subunit folding.
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Affiliation(s)
- J W Kim
- Department of Molecular Biology, College of Natural Sciences, Pusan National University, Pusan, 609-735, Korea
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Frey M, Chomet P, Glawischnig E, Stettner C, Grün S, Winklmair A, Eisenreich W, Bacher A, Meeley RB, Briggs SP, Simcox K, Gierl A. Analysis of a chemical plant defense mechanism in grasses. Science 1997; 277:696-9. [PMID: 9235894 DOI: 10.1126/science.277.5326.696] [Citation(s) in RCA: 397] [Impact Index Per Article: 14.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/04/2023]
Abstract
In the Gramineae, the cyclic hydroxamic acids 2,4-dihydroxy-1, 4-benzoxazin-3-one (DIBOA) and 2,4-dihydroxy-7-methoxy-1, 4-benzoxazin-3-one (DIMBOA) form part of the defense against insects and microbial pathogens. Five genes, Bx1 through Bx5, are required for DIBOA biosynthesis in maize. The functions of these five genes, clustered on chromosome 4, were demonstrated in vitro. Bx1 encodes a tryptophan synthase alpha homolog that catalyzes the formation of indole for the production of secondary metabolites rather than tryptophan, thereby defining the branch point from primary to secondary metabolism. Bx2 through Bx5 encode cytochrome P450-dependent monooxygenases that catalyze four consecutive hydroxylations and one ring expansion to form the highly oxidized DIBOA.
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Affiliation(s)
- M Frey
- Institut für Genetik, Technische Universität München, Lichtenbergstrasse 4, 85747 Garching, Germany
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Yee MC, Horn V, Yanofsky C. On the role of helix 0 of the tryptophan synthetase alpha chain of Escherichia coli. J Biol Chem 1996; 271:14754-63. [PMID: 8662916 DOI: 10.1074/jbc.271.25.14754] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/01/2023] Open
Abstract
The role of helix 0 of the alpha chain (TrpA) of the tryptophan synthetase alpha2beta2 multi-functional enzyme complex of Escherichia coli was examined by deleting amino-terminal residues 2-6, 2-11, or 2-19 of TrpA. Selected substitutions were also introduced at TrpA positions 2-6. The altered genes encoding these polypeptides were overexpressed from a foreign promoter on a multicopy plasmid and following insertion at their normal chromosomal location. Each deletion polypeptide was functional in vivo. However all appeared to be somewhat more labile and insoluble and less active enzymatically than wild type TrpA. The deletion polypeptides were overproduced and solubilized from cell debris by denaturation and refolding. Several were partially purified and assayed in various reactions in the presence of tryptophan synthetase beta2 (TrpB). The purified TrpADelta2-6 and TrpADelta2-11 deletion polypeptides had low activity in both the indole + serine --> tryptophan reaction and the indoleglycerol phosphate + serine --> tryptophan reaction. Poor activity in each reaction was partly due to reduced association of TrpA with TrpB. The addition of the TrpA ligands, alpha-glycerophosphate or indoleglycerol phosphate, during catalysis of the indole + serine --> tryptophan reaction increased association and activity. These findings suggest that removal of helix 0 of TrpA decreases TrpA-TrpB association as well as the activity of the TrpA active site. Alignment of the TrpA sequences from different species indicates that several lack part or all of helix 0. In some of these polypeptides, extra residues at the carboxyl end may substitute for helix 0.
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Affiliation(s)
- M C Yee
- Department of Biological Sciences, Stanford University, Stanford, California, 94305-5020, USA
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Yang X, Miles E. A novel intersubunit repair mechanism in the tryptophan synthase alpha 2 beta 2 complex. Critical role of the beta subunit lysine 167 in intersubunit communication. J Biol Chem 1993. [DOI: 10.1016/s0021-9258(18)41523-2] [Citation(s) in RCA: 11] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/22/2022] Open
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11
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Yang XJ, Ruvinov SB, Miles EW. Overexpression and purification of the separate tryptophan synthase alpha and beta subunits from Salmonella typhimurium. Protein Expr Purif 1992; 3:347-54. [PMID: 1422228 DOI: 10.1016/1046-5928(92)90011-k] [Citation(s) in RCA: 20] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/27/2022]
Abstract
To obtain high levels of expression of the free alpha and beta subunits of tryptophan synthase from Salmonella typhimurium, we have used two plasmids (pStrpA and pStrpB) that carry the genes encoding the alpha and beta subunits, respectively. The expression of each plasmid in Escherichia coli CB149 results in overproduction of each subunit. We also report new and efficient methods for purifying the individual alpha and beta subunits. Microcrystals of the beta subunit are obtained by addition of polyethylene glycol 8000 and spermine to crude bacterial extracts. This crystallization procedure is similar to methods used previously to grow crystals of the S. typhimurium tryptophan synthase alpha 2 beta 2 complex for X-ray crystallography and to purify this complex by crystallization from bacterial extracts. The results suggest that purification by crystallization may be useful for other overexpressed enzymes and multienzymes complexes. Purification of the alpha subunit utilizes ammonium sulfate fractionation, chromatography on diethylaminoethyl-Sephacel, and high-performance liquid chromatography on a Mono Q column. The purified alpha and beta subunits are more than 95% pure by the criterion of sodium dodecyl sulfate gel electrophoresis. The procedures developed can be applied to the expression and purification of mutant forms of the separate alpha and beta subunits. The purified alpha and beta subunits provide useful materials for studies of subunit association and for investigations of other properties of the separate subunits.
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Affiliation(s)
- X J Yang
- Laboratory of Biochemical Pharmacology, National Institute of Diabetes and Digestive and Kidney Diseases, National Institutes of Health, Bethesda, Maryland 20892
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Lim WK, Brouillette C, Hardman JK. Thermal stabilities of mutant Escherichia coli tryptophan synthase alpha subunits. Arch Biochem Biophys 1992; 292:34-41. [PMID: 1727648 DOI: 10.1016/0003-9861(92)90047-z] [Citation(s) in RCA: 14] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/28/2022]
Abstract
Random chemical mutagenesis, in vitro, of the 5' portion of the Escherichia coli trpA gene has yielded 66 mutant alpha subunits containing single amino acid substitutions at 49 different residue sites within the first 121 residues of the protein; this portion of the alpha subunit contains four of the eight alpha helices and three of the eight beta strands in the protein. Sixty-two of the subunits were examined for their heat stabilities by sensitivity to enzymatic inactivation (52 degrees C for 20 min) in crude extracts and by differential scanning calorimetry (DSC) with 29 purified proteins. The enzymatic activities of mutant alpha subunits that contained amino acid substitutions within the alpha and beta secondary structures were more heat labile than the wild-type alpha subunit. Alterations only in three regions, at or immediately C-terminal to the first three beta strands, were stability neutral or stability enhancing with respect to enzymatic inactivation. Enzymatic thermal inactivation appears to be correlated with the relative accessibility of the substituted residues; stability-neutral mutations are found at accessible residual sites, stability-enhancing mutations at buried sites. DSC analyses showed a similar pattern of stabilization/destabilization as indicated by inactivation studies. Tm differences from the wild-type alpha subunit varied +/- 7.6 degrees C. Eighteen mutant proteins containing alterations in helical and sheet structures had Tm's significantly lower (-1.6 to -7.5 degrees C) than the wild-type Tm (59.5 degrees C). In contrast, 6 mutant alpha subunits with alterations in the regions following beta strands 1 and 3 had increased Tm's (+1.4 to +7.6 degrees C). Because of incomplete thermal reversibilities for many of the mutant alpha subunits, most likely due to identifiable aggregated forms in the unfolded state, reliable differences in thermodynamic stability parameters are not possible. The availability of this group of mutant alpha subunits which clearly contain structural alterations should prove useful in defining the roles of certain residues or sequences in the unfolding/folding pathway for this protein when examined by urea/guaninidine denaturation kinetic analysis.
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Affiliation(s)
- W K Lim
- Department of Biological Sciences, University of Alabama, Tuscaloosa 35487
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Lim W, Sarkar S, Hardman J. Enzymatic properties of mutant Escherichia coli tryptophan synthase alpha-subunits. J Biol Chem 1991. [DOI: 10.1016/s0021-9258(18)54910-3] [Citation(s) in RCA: 20] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/26/2022] Open
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