3BGD

Thiopurine S-Methyltransferase

3BGD の概要

• エントリーDOI: 10.2210/pdb3bgd/pdb
• 関連するPDBエントリー: 3BGI 3BKE 3BKO
• 分子名称: Thiopurine S-methyltransferase, S-ADENOSYL-L-HOMOCYSTEINE, 9H-purine-6-thiol, ... (4 entities in total)
• 機能のキーワード: methyltransferase, cytoplasm, s-adenosyl-l-methionine, transferase
• 由来する生物種: Mus musculus (Mouse)
• 細胞内の位置: Cytoplasm: O55060
• タンパク質・核酸の鎖数: 2
• 化学式量合計: 60969.68

構造登録者

Peng, Y.,Yee, V.C. (登録日: 2007-11-26, 公開日: 2008-06-10, 最終更新日: 2024-02-21)

主引用文献

Peng, Y.,Feng, Q.,Wilk, D.,Adjei, A.A.,Salavaggione, O.E.,Weinshilboum, R.M.,Yee, V.C.
Structural Basis of Substrate Recognition in Thiopurine S-Methyltransferase
Biochemistry, 47 (23), 6216 6225, 2008. 10.1021/bi800102x:6216-6225, 2008

PubMed Abstract: Thiopurine S-methyltransferase (TPMT) modulates the cytotoxic effects of thiopurine prodrugs such as 6-mercaptopurine by methylating them in a reaction using S-adenosyl- l-methionine as the donor. Patients with TPMT variant allozymes exhibit diminished levels of protein and/or enzyme activity and are at risk for thiopurine drug-induced toxicity. We have determined two crystal structures of murine TPMT, as a binary complex with the product S-adenosyl- l-homocysteine and as a ternary complex with S-adenosyl- l-homocysteine and the substrate 6-mercaptopurine, to 1.8 and 2.0 A resolution, respectively. Comparison of the structures reveals that an active site loop becomes ordered upon 6-mercaptopurine binding. The positions of the two ligands are consistent with the expected S N2 reaction mechanism. Arg147 and Arg221, the only polar amino acids near 6-mercaptopurine, are highlighted as possible participants in substrate deprotonation. To probe whether these residues are important for catalysis, point mutants were prepared in the human enzyme. Substitution of Arg152 (Arg147 in murine TPMT) with glutamic acid decreases V max and increases K m for 6-mercaptopurine but not K m for S-adenosyl- l-methionine. Substitution at this position with alanine or histidine and similar substitutions of Arg226 (Arg221 in murine TPMT) result in no effect on enzyme activity. The double mutant Arg152Ala/Arg226Ala exhibits a decreased V max and increased K m for 6-mercaptopurine. These observations suggest that either Arg152 or Arg226 may participate in some fashion in the TPMT reaction, with one residue compensating when the other is altered, and that Arg152 may interact with substrate more directly than Arg226, consistent with observations in the murine TPMT crystal structure.

PubMed: 18484748
DOI: 10.1021/bi800102x

実験手法

X-RAY DIFFRACTION (2 Å)