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Vuksanovic N, Melkonian TR, Serrano DA, Schwabacher AW, Silvaggi NR. Structural and Biochemical Characterization of MppQ, an L-Enduracididine Biosynthetic Enzyme from Streptomyces hygroscopicus. Biochemistry 2023; 62:3105-3115. [PMID: 37890134 DOI: 10.1021/acs.biochem.3c00428] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/29/2023]
Abstract
MppQ is an enzyme of unknown function from Streptomyces hygroscopicus (ShMppQ) that operates in the biosynthesis of the nonproteinogenic amino acid L-enduracididine (L-End). Since L-End is a component of several peptides showing activity against antibiotic-resistant pathogens, understanding its biosynthetic pathway could facilitate the development of chemoenzymatic routes to novel antibiotics. Herein, we report on the crystal structures of ShMppQ complexed with pyridoxal-5'-phosphate (PLP) and pyridoxamine-5'-phosphate (PMP). ShMppQ is similar to fold-type I PLP-dependent aminotransferases like aspartate aminotransferase. The tertiary structure of ShMppQ is composed of an N-terminal extension, a large domain, and a small domain. The active site is placed at the junction of the large and small domains and includes residues from both protomers of the homodimer. We also report the first functional characterization of MppQ, which we incubated with the enzymatically produced 2-ketoenduracidine and observed the conversion to L-End, establishing ShMppQ as the final enzyme in L-End biosynthesis. Additionally, we have observed that MppQ has a relatively high affinity for 2-keto-5-guanidinovaleric acid (i.e., 2-ketoarginine), a shunt product of MppP, indicating the potential role of MppQ in increasing the efficiency of L-End biosynthesis by converting 2-ketoarginine back to the starting material, l-arginine. A panel of potential amino-donor substrates was tested for the transamination activity against a saturating concentration of 2-ketoarginine in end-point assays. Most l-Arg was produced with l-ornithine as the donor substrate. Steady-state kinetic analysis of the transamination reaction with l-Orn and 2-ketoarginine shows that the kinetic constants are in line with those for the amino donor substrate of other fold-type I aminotransferases.
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Affiliation(s)
- Nemanja Vuksanovic
- Department of Chemistry and Biochemistry, University of Wisconsin-Milwaukee, 3210 North Cramer Street, Milwaukee, Wisconsin 53211, United States
- Department of Chemistry, Boston University, 590 Commonwealth Avenue, Boston, Massachusetts 02215, United States
| | - Trevor R Melkonian
- Department of Chemistry and Biochemistry, University of Wisconsin-Milwaukee, 3210 North Cramer Street, Milwaukee, Wisconsin 53211, United States
- Division of Chemical Biology and Medicinal Chemistry, The University of Texas at Austin, Austin, Texas 78712, United States
| | - Dante A Serrano
- Department of Chemistry and Biochemistry, University of Wisconsin-Milwaukee, 3210 North Cramer Street, Milwaukee, Wisconsin 53211, United States
- Department of Chemistry, Pennsylvania State University, 302 Chemistry Building, University Park, Pennsylvania 16802, United States
| | - Alan W Schwabacher
- Department of Chemistry and Biochemistry, University of Wisconsin-Milwaukee, 3210 North Cramer Street, Milwaukee, Wisconsin 53211, United States
| | - Nicholas R Silvaggi
- Department of Chemistry and Biochemistry, University of Wisconsin-Milwaukee, 3210 North Cramer Street, Milwaukee, Wisconsin 53211, United States
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Li S, Shao Z, Lu C, Duan D. Isolation and functional verification of an aspartate aminotransferase gene from Neoporphyra haitanensis. BMC PLANT BIOLOGY 2023; 23:150. [PMID: 36941626 PMCID: PMC10029208 DOI: 10.1186/s12870-023-04158-2] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Figures] [Subscribe] [Scholar Register] [Received: 11/30/2022] [Accepted: 03/08/2023] [Indexed: 06/18/2023]
Abstract
BACKGROUND Neoporphyra haitanensis is a commercial laver species in China. Aspartic acid is an important flavor amino acid, and aspartate aminotransferase (AAT) is a crucial enzyme in its biosynthesis. In this study, we cloned one AAT gene (NhAAT) from the red alga N. haitanensis and investigated its sequence structure, transcriptional expression and enzymatic characteristics. The purpose of our research is to obtain a functional AAT responsible for the biosynthesis of aspartic acid from red seaweeds, which has the potential to influence the flavor of N. haitanensis. RESULTS Sequence analysis showed that NhAAT contains a conserved domain of Aminotran_1_2, which belongs to the transaminase superfamily. The secondary structure of NhAAT is dominated by α-helix. The results of enzymatic characterization illustrated that the NhAAT has highest catalytic activity at 45 °C and pH 7.5 in both forward and reverse reactions. The calculated Km values of NhAAT was 5.67 and 6.16 mM for L-glutamic acid and L-aspartic acid, respectively. Quantitative analysis showed that the NhAAT expression of N. haitanensis collected in late harvest (Dec) was 4.5 times that of N. haitanensis collected in early harvest (Oct), while the aspartic acid content of N. haitanensis collected in late harvest (Dec) was 1.2 times that of N. haitanensis collected in early harvest (Oct). CONCLUSION The results of enzyme kinetics indicated that NhAAT prefers to catalyze the reaction in the direction of aspartic acid production. Moreover, the trend of NhAAT expression level was consistent with that of aspartic acid content in N. haitanensis in different harvest periods. Our research is helpful to understand the accumulation and regulation of amino acids in N. haitanensis in different habitats and the taste difference of N. haitanensis in different harvest periods.
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Affiliation(s)
- Shuang Li
- CAS and Shandong Province Key Laboratory of Experimental Marine Biology, Center for Ocean Mega-Science, Institute of Oceanology, Chinese Academy of Sciences, Qingdao, 266071, China
- Laboratory for Marine Biology and Biotechnology, Qingdao National Laboratory for Marine Science and Technology, Qingdao, 266237, China
- University of Chinese Academy of Sciences, Beijing, 100049, China
| | - Zhanru Shao
- CAS and Shandong Province Key Laboratory of Experimental Marine Biology, Center for Ocean Mega-Science, Institute of Oceanology, Chinese Academy of Sciences, Qingdao, 266071, China.
- Laboratory for Marine Biology and Biotechnology, Qingdao National Laboratory for Marine Science and Technology, Qingdao, 266237, China.
| | - Chang Lu
- Department of Biological Engineering, College of Life Science, Yantai University, Yantai, 264005, P. R. China
| | - Delin Duan
- CAS and Shandong Province Key Laboratory of Experimental Marine Biology, Center for Ocean Mega-Science, Institute of Oceanology, Chinese Academy of Sciences, Qingdao, 266071, China.
- Laboratory for Marine Biology and Biotechnology, Qingdao National Laboratory for Marine Science and Technology, Qingdao, 266237, China.
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Choi M, Rhee S. Structural and biochemical basis for the substrate specificity of Pad-1, an indole-3-pyruvic acid aminotransferase in auxin homeostasis. J Struct Biol 2022; 214:107857. [PMID: 35395410 DOI: 10.1016/j.jsb.2022.107857] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/17/2021] [Revised: 02/15/2022] [Accepted: 04/01/2022] [Indexed: 11/18/2022]
Abstract
Phytohormone indole-3-acetic acid (IAA) plays a vital role in regulating plant growth and development. Tryptophan-dependent IAA biosynthesis participates in IAA homeostasis by producing IAA via two sequential reactions, which involve a conversion of tryptophan to indole-3-pyruvic acid (IPyA) by tryptophan aminotransferase (TAA1) followed by the irreversible formation of IAA in the second reaction. Pad-1 from Solanaceae plants regulates IAA levels by catalyzing a reverse reaction of the first step of IAA biosynthesis. Pad-1 is a pyridoxal phosphate (PLP)-dependent aminotransferase, with IPyA as the amino acceptor and l-glutamine as the amino donor. Currently, the structural and functional basis for the substrate specificity of Pad-1 remains poorly understood. In this study, we carried out structural and kinetic analyses of Pad-1 from Solanum melongena. Pad-1 is a homodimeric enzyme, with coenzyme PLP present between a central large α/β domain and a protruding small domain. The active site of Pad-1 includes a vacancy near the phosphate group (P-side) and the 3'-O (O-side) of PLP. These features are distinct from those of TAA1, which is homologous in an overall structure with Pad-1 but includes only the P-side region in the active site. Kinetic analysis suggests that P-side residues constitute a binding pocket for l-glutamine, and O-side residues of Phe124 and Ile350 are involved in the binding of IPyA. These studies illuminate distinct differences in the active site between Pad-1 and TAA1, and provide structural and functional insights into the substrate specificity of Pad-1.
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Affiliation(s)
- Minyoung Choi
- Department of Agricultural Biotechnology, Seoul National University, Seoul, Republic of Korea
| | - Sangkee Rhee
- Department of Agricultural Biotechnology, Seoul National University, Seoul, Republic of Korea; Research Institute of Agriculture and Life Sciences, Seoul National University, Seoul, Republic of Korea.
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Weatherhead AW, Crowther JM, Horne CR, Meng Y, Coombes D, Currie MJ, Watkin SAJ, Adams LE, Parthasarathy A, Dobson RCJ, Hudson AO. Structure-Function Studies of the Antibiotic Target l,l-Diaminopimelate Aminotransferase from Verrucomicrobium spinosum Reveal an Unusual Oligomeric Structure. Biochemistry 2020; 59:2274-2288. [PMID: 32478518 DOI: 10.1021/acs.biochem.0c00185] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
Abstract
While humans lack the biosynthetic pathways for meso-diaminopimelate and l-lysine, they are essential for bacterial survival and are therefore attractive targets for antibiotics. It was recently discovered that members of the Chlamydia family utilize a rare aminotransferase route of the l-lysine biosynthetic pathway, thus offering a new enzymatic drug target. Here we characterize diaminopimelate aminotransferase from Verrucomicrobium spinosum (VsDapL), a nonpathogenic model bacterium for Chlamydia trachomatis. Complementation experiments verify that the V. spinosum dapL gene encodes a bona fide diaminopimelate aminotransferase, because the gene rescues an Escherichia coli strain that is auxotrophic for meso-diaminopimelate. Kinetic studies show that VsDapL follows a Michaelis-Menten mechanism, with a KMapp of 4.0 mM toward its substrate l,l-diaminopimelate. The kcat (0.46 s-1) and the kcat/KM (115 s-1 M-1) are somewhat lower than values for other diaminopimelate aminotransferases. Moreover, whereas other studied DapL orthologs are dimeric, sedimentation velocity experiments demonstrate that VsDapL exists in a monomer-dimer self-association, with a KD2-1 of 7.4 μM. The 2.25 Å resolution crystal structure presents the canonical dimer of chalice-shaped monomers, and small-angle X-ray scattering experiments confirm the dimer in solution. Sequence and structural alignments reveal that active site residues important for activity are conserved in VsDapL, despite the lower activity compared to those of other DapL homologues. Although the dimer interface buries 18% of the total surface area, several loops that contribute to the interface and active site, notably the L1, L2, and L5 loops, are highly mobile, perhaps explaining the unstable dimer and lower catalytic activity. Our kinetic, biophysical, and structural characterization can be used to inform the development of antibiotics.
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Affiliation(s)
- Anthony W Weatherhead
- Biomolecular Interaction Centre and School of Biological Sciences, University of Canterbury, P.O. Box 4800, Christchurch 8140, New Zealand
| | - Jennifer M Crowther
- Biomolecular Interaction Centre and School of Biological Sciences, University of Canterbury, P.O. Box 4800, Christchurch 8140, New Zealand
| | - Christopher R Horne
- Biomolecular Interaction Centre and School of Biological Sciences, University of Canterbury, P.O. Box 4800, Christchurch 8140, New Zealand
| | - Yanxiang Meng
- Biomolecular Interaction Centre and School of Biological Sciences, University of Canterbury, P.O. Box 4800, Christchurch 8140, New Zealand
| | - David Coombes
- Biomolecular Interaction Centre and School of Biological Sciences, University of Canterbury, P.O. Box 4800, Christchurch 8140, New Zealand
| | - Michael J Currie
- Biomolecular Interaction Centre and School of Biological Sciences, University of Canterbury, P.O. Box 4800, Christchurch 8140, New Zealand
| | - Serena A J Watkin
- Biomolecular Interaction Centre and School of Biological Sciences, University of Canterbury, P.O. Box 4800, Christchurch 8140, New Zealand
| | - Lily E Adams
- Thomas H. Gosnell School of Life Sciences, Rochester Institute of Technology, Rochester, New York 14623-5603, United States
| | - Anutthaman Parthasarathy
- Thomas H. Gosnell School of Life Sciences, Rochester Institute of Technology, Rochester, New York 14623-5603, United States
| | - Renwick C J Dobson
- Biomolecular Interaction Centre and School of Biological Sciences, University of Canterbury, P.O. Box 4800, Christchurch 8140, New Zealand.,Bio21 Molecular Science and Biotechnology Institute, Department of Biochemistry and Molecular Biology, University of Melbourne, Parkville, Victoria 3010, Australia
| | - André O Hudson
- Thomas H. Gosnell School of Life Sciences, Rochester Institute of Technology, Rochester, New York 14623-5603, United States
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Son HF, Kim KJ. Structural Insights into a Novel Class of Aspartate Aminotransferase from Corynebacterium glutamicum. PLoS One 2016; 11:e0158402. [PMID: 27355211 PMCID: PMC4927141 DOI: 10.1371/journal.pone.0158402] [Citation(s) in RCA: 11] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/22/2015] [Accepted: 06/15/2016] [Indexed: 11/18/2022] Open
Abstract
Aspartate aminotransferase from Corynebacterium glutamicum (CgAspAT) is a PLP-dependent enzyme that catalyzes the production of L-aspartate and α-ketoglutarate from L-glutamate and oxaloacetate in L-lysine biosynthesis. In order to understand the molecular mechanism of CgAspAT and compare it with those of other aspartate aminotransferases (AspATs) from the aminotransferase class I, we determined the crystal structure of CgAspAT. CgAspAT functions as a dimer, and the CgAspAT monomer consists of two domains, the core domain and the auxiliary domain. The PLP cofactor is found to be bound to CgAspAT and stabilized through unique residues. In our current structure, a citrate molecule is bound at the active site of one molecule and mimics binding of the glutamate substrate. The residues involved in binding of the PLP cofactor and the glutamate substrate were confirmed by site-directed mutagenesis. Interestingly, compared with other AspATs from aminotransferase subgroup Ia and Ib, CgAspAT exhibited unique binding sites for both cofactor and substrate; moreover, it was found to have unusual structural features in the auxiliary domain. Based on these structural differences, we propose that CgAspAT does not belong to either subgroup Ia or Ib, and can be categorized into a subgroup Ic. The phylogenetic tree and RMSD analysis also indicates that CgAspAT is located in an independent AspAT subgroup.
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Affiliation(s)
- Hyeoncheol Francis Son
- School of Life Sciences, KNU Creative BioResearch Group, Kyungpook National University, Daehak-ro 80, Buk-ku, Daegu 702–701, Korea
| | - Kyung-Jin Kim
- School of Life Sciences, KNU Creative BioResearch Group, Kyungpook National University, Daehak-ro 80, Buk-ku, Daegu 702–701, Korea
- * E-mail:
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Bujacz A, Rutkiewicz-Krotewicz M, Nowakowska-Sapota K, Turkiewicz M. Crystal structure and enzymatic properties of a broad substrate-specificity psychrophilic aminotransferase from the Antarctic soil bacterium Psychrobacter sp. B6. ACTA ACUST UNITED AC 2015; 71:632-45. [PMID: 25760611 DOI: 10.1107/s1399004714028016] [Citation(s) in RCA: 12] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/19/2014] [Accepted: 12/23/2014] [Indexed: 12/20/2022]
Abstract
Aminotransferases (ATs) are enzymes that are commonly used in the chemical and pharmaceutical industries for the synthesis of natural and non-natural amino acids by transamination reactions. Currently, the easily accessible enzymes from mesophilic organisms are most commonly used; however, for economical and ecological reasons the utilization of aminotransferases from psychrophiles would be more advantageous, as their optimum reaction temperature is usually significantly lower than for the mesophilic ATs. Here, gene isolation, protein expression, purification, enzymatic properties and structural studies are reported for the cold-active aromatic amino-acid aminotransferase (PsyArAT) from Psychrobacter sp. B6, a psychrotrophic, Gram-negative strain from Antarctic soil. Preliminary computational analysis indicated dual functionality of the enzyme through the ability to utilize both aromatic amino acids and aspartate as substrates. This postulation was confirmed by enzymatic activity tests, which showed that it belonged to the class EC 2.6.1.57. The first crystal structures of a psychrophilic aromatic amino-acid aminotransferase have been determined at resolutions of 2.19 Å for the native enzyme (PsyArAT) and 2.76 Å for its complex with aspartic acid (PsyArAT/D). Both types of crystals grew in the monoclinic space group P21 under slightly different crystallization conditions. The PsyArAT crystals contained a dimer (90 kDa) in the asymmetric unit, which corresponds to the active form of this enzyme, whereas the crystals of the PsyArAT/D complex included four dimers showing different stages of the transamination reaction.
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Affiliation(s)
- Anna Bujacz
- Institute of Technical Biochemistry, Lodz University of Technology, Stefanowskiego 4/10, 90-924 Lodz, Poland
| | - Maria Rutkiewicz-Krotewicz
- Institute of Technical Biochemistry, Lodz University of Technology, Stefanowskiego 4/10, 90-924 Lodz, Poland
| | - Karolina Nowakowska-Sapota
- Institute of Technical Biochemistry, Lodz University of Technology, Stefanowskiego 4/10, 90-924 Lodz, Poland
| | - Marianna Turkiewicz
- Institute of Technical Biochemistry, Lodz University of Technology, Stefanowskiego 4/10, 90-924 Lodz, Poland
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Thomsen M, Skalden L, Palm GJ, Höhne M, Bornscheuer UT, Hinrichs W. Crystallographic characterization of the (R)-selective amine transaminase from Aspergillus fumigatus. ACTA ACUST UNITED AC 2014; 70:1086-93. [PMID: 24699652 DOI: 10.1107/s1399004714001084] [Citation(s) in RCA: 29] [Impact Index Per Article: 2.9] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/19/2013] [Accepted: 01/15/2014] [Indexed: 11/10/2022]
Abstract
The importance of amine transaminases for producing optically pure chiral precursors for pharmaceuticals and chemicals has substantially increased in recent years. The X-ray crystal structure of the (R)-selective amine transaminase from the fungus Aspergillus fumigatus was solved by S-SAD phasing to 1.84 Å resolution. The refined structure at 1.27 Å resolution provides detailed knowledge about the molecular basis of substrate recognition and conversion to facilitate protein-engineering approaches. The protein forms a homodimer and belongs to fold class IV of the pyridoxal-5'-phosphate-dependent enzymes. Both subunits contribute residues to form two active sites. The structure of the holoenzyme shows the catalytically important cofactor pyridoxal-5'-phosphate bound as an internal aldimine with the catalytically responsible amino-acid residue Lys179, as well as in its free form. A long N-terminal helix is an important feature for the stability of this fungal (R)-selective amine transaminase, but is missing in branched-chain amino-acid aminotransferases and D-amino-acid aminotransferases.
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Affiliation(s)
- Maren Thomsen
- Institute of Biochemistry, University of Greifswald, Felix-Hausdorff-Strasse 4, 17489 Greifswald, Germany
| | - Lilly Skalden
- Institute of Biochemistry, University of Greifswald, Felix-Hausdorff-Strasse 4, 17489 Greifswald, Germany
| | - Gottfried J Palm
- Institute of Biochemistry, University of Greifswald, Felix-Hausdorff-Strasse 4, 17489 Greifswald, Germany
| | - Matthias Höhne
- Institute of Biochemistry, University of Greifswald, Felix-Hausdorff-Strasse 4, 17489 Greifswald, Germany
| | - Uwe T Bornscheuer
- Institute of Biochemistry, University of Greifswald, Felix-Hausdorff-Strasse 4, 17489 Greifswald, Germany
| | - Winfried Hinrichs
- Institute of Biochemistry, University of Greifswald, Felix-Hausdorff-Strasse 4, 17489 Greifswald, Germany
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Thomsen M, Skalden L, Palm GJ, Höhne M, Bornscheuer UT, Hinrichs W. Crystallization and preliminary X-ray diffraction studies of the (R)-selective amine transaminase from Aspergillus fumigatus. Acta Crystallogr Sect F Struct Biol Cryst Commun 2013; 69:1415-7. [PMID: 24316843 PMCID: PMC3855733 DOI: 10.1107/s1744309113030923] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/04/2013] [Accepted: 11/11/2013] [Indexed: 11/11/2022]
Abstract
The (R)-selective amine transaminase from Aspergillus fumigatus was expressed in Escherichia coli and purified to homogeneity. Bright yellow crystals appeared while storing the concentrated solution in the refrigerator and belonged to space group C222(1). X-ray diffraction data were collected to 1.27 Å resolution, as well as an anomalous data set to 1.84 Å resolution that was suitable for S-SAD phasing.
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Affiliation(s)
- Maren Thomsen
- Institut für Biochemie, Universität Greifswald, Felix-Hausdorff-Strasse 4, D-17489 Greifswald, Germany
| | - Lilly Skalden
- Institut für Biochemie, Universität Greifswald, Felix-Hausdorff-Strasse 4, D-17489 Greifswald, Germany
| | - Gottfried J. Palm
- Institut für Biochemie, Universität Greifswald, Felix-Hausdorff-Strasse 4, D-17489 Greifswald, Germany
| | - Matthias Höhne
- Institut für Biochemie, Universität Greifswald, Felix-Hausdorff-Strasse 4, D-17489 Greifswald, Germany
| | - Uwe T. Bornscheuer
- Institut für Biochemie, Universität Greifswald, Felix-Hausdorff-Strasse 4, D-17489 Greifswald, Germany
| | - Winfried Hinrichs
- Institut für Biochemie, Universität Greifswald, Felix-Hausdorff-Strasse 4, D-17489 Greifswald, Germany
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Duff SM, Rydel TJ, McClerren AL, Zhang W, Li JY, Sturman EJ, Halls C, Chen S, Zeng J, Peng J, Kretzler CN, Evdokimov A. The Enzymology of alanine aminotransferase (AlaAT) isoforms from Hordeum vulgare and other organisms, and the HvAlaAT crystal structure. Arch Biochem Biophys 2012; 528:90-101. [DOI: 10.1016/j.abb.2012.06.006] [Citation(s) in RCA: 25] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/26/2012] [Revised: 06/19/2012] [Accepted: 06/20/2012] [Indexed: 11/15/2022]
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Wu HJ, Yang Y, Wang S, Qiao JQ, Xia YF, Wang Y, Wang WD, Gao SF, Liu J, Xue PQ, Gao XW. Cloning, expression and characterization of a new aspartate aminotransferase from Bacillus subtilis B3. FEBS J 2011; 278:1345-57. [PMID: 21332942 DOI: 10.1111/j.1742-4658.2011.08054.x] [Citation(s) in RCA: 13] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/26/2022]
Abstract
In the present study, we report the identification of a new gene from the Bacillus subtilis B3 strain (aatB3), which comprises 1308 bp encoding a 436 amino acid protein with a monomer molecular weight of 49.1 kDa. Phylogenetic analyses suggested that this enzyme is a member of the Ib subgroup of aspartate aminotransferases (AATs; EC 2.6.1.1), although it also has conserved active residues and thermostability characteristic of Ia-type AATs. The Asp232, Lys270 and Arg403 residues of AATB3 play a key role in transamination. The enzyme showed maximal activity at pH 8.0 and 45 °C, had relatively high activity over an alkaline pH range (pH 7.0-9.0) and was stable up to 50 °C. AATB3 catalyzed the transamination of five amino acids, with L-aspartate being the optimal substrate. The K(m) values were determined to be 6.7 mM for L-aspartate, 0.3 mM for α-ketoglutarate, 8.0 mM for L-glutamate and 0.6 mM for oxaloacetate. A 32-residue N-terminal amino acid sequence of this enzyme has 53% identity with that of Bacillus circulans AAT, although it is absent in all other AATs from different organisms. Further studies on AATB3 may confirm that it is potentially beneficial in basic research as well as various industrial applications.
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Affiliation(s)
- Hui-Jun Wu
- Department of Plant Pathology, College of Plant Protection, Nanjing Agricultural University, Key Laboratory of Monitoring and Management of Crop Diseases and Pest Insects, Ministry of Agriculture, Nanjing, China
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Crystal Structure of MJ0684 from Methanococcus jannaschii, a Novel Archaeal Homolog of Kynurenine Aminotransferase. B KOREAN CHEM SOC 2008. [DOI: 10.5012/bkcs.2008.29.1.173] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022]
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12
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Watanabe N, Cherney MM, van Belkum MJ, Marcus SL, Flegel MD, Clay MD, Deyholos MK, Vederas JC, James MNG. Crystal Structure of ll-Diaminopimelate Aminotransferase from Arabidopsis thaliana: A Recently Discovered Enzyme in the Biosynthesis of l-Lysine by Plants and Chlamydia. J Mol Biol 2007; 371:685-702. [PMID: 17583737 DOI: 10.1016/j.jmb.2007.05.061] [Citation(s) in RCA: 37] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/13/2007] [Revised: 05/21/2007] [Accepted: 05/22/2007] [Indexed: 11/18/2022]
Abstract
The essential biosynthetic pathway to l-Lysine in bacteria and plants is an attractive target for the development of new antibiotics or herbicides because it is absent in humans, who must acquire this amino acid in their diet. Plants use a shortcut of a bacterial pathway to l-Lysine in which the pyridoxal-5'-phosphate (PLP)-dependent enzyme ll-diaminopimelate aminotransferase (LL-DAP-AT) transforms l-tetrahydrodipicolinic acid (L-THDP) directly to LL-DAP. In addition, LL-DAP-AT was recently found in Chlamydia sp., suggesting that inhibitors of this enzyme may also be effective against such organisms. In order to understand the mechanism of this enzyme and to assist in the design of inhibitors, the three-dimensional crystal structure of LL-DAP-AT was determined at 1.95 A resolution. The cDNA sequence of LL-DAP-AT from Arabidopsis thaliana (AtDAP-AT) was optimized for expression in bacteria and cloned in Escherichia coli without its leader sequence but with a C-terminal hexahistidine affinity tag to aid protein purification. The structure of AtDAP-AT was determined using the multiple-wavelength anomalous dispersion (MAD) method with a seleno-methionine derivative. AtDAP-AT is active as a homodimer with each subunit having PLP in the active site. It belongs to the family of type I fold PLP-dependent enzymes. Comparison of the active site residues of AtDAP-AT and aspartate aminotransferases revealed that the PLP binding residues in AtDAP-AT are well conserved in both enzymes. However, Glu97* and Asn309* in the active site of AtDAP-AT are not found at similar positions in aspartate aminotransferases, suggesting that specific substrate recognition may require these residues from the other monomer. A malate-bound structure of AtDAP-AT allowed LL-DAP and L-glutamate to be modelled into the active site. These initial three-dimensional structures of LL-DAP-AT provide insight into its substrate specificity and catalytic mechanism.
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Affiliation(s)
- Nobuhiko Watanabe
- Group in Protein Structure and Function, Department of Biochemistry, University of Alberta, Edmonton, Alberta, Canada
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Conners SB, Mongodin EF, Johnson MR, Montero CI, Nelson KE, Kelly RM. Microbial biochemistry, physiology, and biotechnology of hyperthermophilic Thermotoga species. FEMS Microbiol Rev 2006; 30:872-905. [PMID: 17064285 DOI: 10.1111/j.1574-6976.2006.00039.x] [Citation(s) in RCA: 90] [Impact Index Per Article: 5.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/16/2023] Open
Abstract
High-throughput sequencing of microbial genomes has allowed the application of functional genomics methods to species lacking well-developed genetic systems. For the model hyperthermophile Thermotoga maritima, microarrays have been used in comparative genomic hybridization studies to investigate diversity among Thermotoga species. Transcriptional data have assisted in prediction of pathways for carbohydrate utilization, iron-sulfur cluster synthesis and repair, expolysaccharide formation, and quorum sensing. Structural genomics efforts aimed at the T. maritima proteome have yielded hundreds of high-resolution datasets and predicted functions for uncharacterized proteins. The information gained from genomics studies will be particularly useful for developing new biotechnology applications for T. maritima enzymes.
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Affiliation(s)
- Shannon B Conners
- Department of Chemical and Biomolecular Engineering, North Carolina State University, Raleigh, NC 27695-7905, USA
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Page R, Deacon AM, Lesley SA, Stevens RC. Shotgun crystallization strategy for structural genomics II: crystallization conditions that produce high resolution structures for T. maritima proteins. ACTA ACUST UNITED AC 2006; 6:209-17. [PMID: 16211521 DOI: 10.1007/s10969-005-1916-7] [Citation(s) in RCA: 13] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/03/2004] [Accepted: 01/16/2005] [Indexed: 11/27/2022]
Abstract
Currently, 119 high resolution structures of Thermotoga maritima proteins have been determined by the Joint Center for Structural Genomics (JCSG, www.jcsg.org). Sixty-seven of these were solved using the first implementation of the multi-tiered crystallization strategy at the JCSG for the efficient crystallization of large numbers of protein targets. Previously, we reported the analysis of all proteins crystallized using this multi-tiered strategy [Lesley, S.A. et al. (2002) Proc. Natl. Acad. Sci. USA 99, 11664-11669; Page, R. et al. (2003) Acta Crystallogr. D Biol. Crystallogr. 59, 1028-1037]. Here, we extend the analysis and describe the crystallization characteristics of those proteins that produced diffraction quality crystals, ultimately resulting in high resolution structures. First, we found that over 77% (52) of the crystals used for structure determination were produced directly from high-throughput coarse screens, indicating that less than one quarter of the crystals (15) required fine screening. In addition, as observed for the proteome screen [Page, R. et al. (2003) Acta Crystallogr. D Biol. Crystallogr. 59, 1028-1037], the majority of conditions that produced crystals for natively expressed proteins, whose structures have been determined, were distinct from those of their more extensively purified and selenomethionine-labeled counterparts. Finally, 99% of the proteins whose structures were solved crystallized in conditions contained in the JCSG Minimal Core Screen [Page, R. et al. (2003) Acta Crystallogr. D Biol. Crystallogr. 59, 1028-1037; Page, R. and Stevens, R.C. (2004) Methods 34, 373-389], a set of 67 conditions previously identified as those most likely to produce crystals of a diverse set of proteins, confirming its success for rapid identification of proteins with a natural propensity to crystallize.
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