1GTU
LIGAND-FREE HUMAN GLUTATHIONE S-TRANSFERASE M1A-1A
1GTU の概要
エントリーDOI | 10.2210/pdb1gtu/pdb |
分子名称 | GLUTATHIONE S-TRANSFERASE (2 entities in total) |
機能のキーワード | transferase, glutathione, conjugation, detoxification, cytosolic, dimer |
由来する生物種 | Homo sapiens (human) |
細胞内の位置 | Cytoplasm: P09488 |
タンパク質・核酸の鎖数 | 4 |
化学式量合計 | 102462.58 |
構造登録者 | Patskovsky, Y.V.,Patskovska, L.N.,Listowsky, I. (登録日: 1998-06-11, 公開日: 1999-02-02, 最終更新日: 2024-05-22) |
主引用文献 | Patskovsky, Y.V.,Patskovska, L.N.,Listowsky, I. Functions of His107 in the catalytic mechanism of human glutathione S-transferase hGSTM1a-1a. Biochemistry, 38:1193-1202, 1999 Cited by PubMed Abstract: Domain interchange analyses and site-directed mutagenesis indicate that the His107 residue of the human subunit hGSTM1 has a pronounced influence on catalysis of nucleophilic aromatic substitution reactions, and a H107S substitution accounts for the marked differences in the properties of the homologous hGSTM1-1 (His107) and hGSTM4-4 (Ser107) glutathione S-transferases. Reciprocal replacement of His107 and Ser107 in chimeric enzymes results in reciprocal conversion of catalytic properties. With 1-chloro-2, 4-dinitrobenzene as a substrate, the His107 residue primarily influences the pH dependence of catalysis by lowering the apparent pKa of kcat/Km from 7.8 for the Ser107-containing enzymes to 6.3 for the His107-containing enzymes. There is a parallel shift in the pKa for thiolate anion formation of enzyme-bound GSH. Y6F mutations have no effect on the pKa for these enzymes. Crystal structures of hGSTM1a-1a indicate that the imidazole ring of His107 is oriented toward the substrate binding cleft approximately 6 A from the GSH thiol group. Thus, His107 has the potential to act as a general base in proton transfer mediated through an active site water molecule or directly following a modest conformational change, to promote thiolate anion formation. All wild-type enzymes and H107S chimera have nearly identical equilibrium constants for formation of enzyme-GSH complexes (Kd values of 1-2 x 10(-)6 M); however, KmGSH and Ki values for S-methylglutathione inhibition determined by steady-state kinetics are nearly 100-fold higher. The functions of His107 of hGSTM1a-1a are unexpected in view of a substantial body of previous evidence that excluded participation of histidine residues in the catalytic mechanisms of other glutathione S-transferases. Consequences of His107 involvement in catalysis are also substrate-dependent; in contrast to 1-chloro-2,4-dinitrobenzene, for the nucleophilic addition reaction of GSH to ethacrynic acid, the H107S substitution has no effect on catalysis presumably because product release is rate-limiting. PubMed: 9930979DOI: 10.1021/bi982164m 主引用文献が同じPDBエントリー |
実験手法 | X-RAY DIFFRACTION (2.68 Å) |
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