5H02

Crystal structure of Methanohalophilus portucalensis glycine sarcosine N-methyltransferase tetramutant (H21G, E23T, E24N, L28S)

5H02 の概要

• エントリーDOI: 10.2210/pdb5h02/pdb
• 分子名称: Glycine sarcosine N-methyltransferase, S-ADENOSYL-L-HOMOCYSTEINE, TRIMETHYL GLYCINE, ... (4 entities in total)
• 機能のキーワード: s-adenosylmethionine-dependent methyltransferases, sam, adomet-mtase, class i monomethylation, glycine, sarcosine, rate-limiting enzyme, betaine biosynthesis, betaine-mediated feedback inhibition, transferase
• 由来する生物種: Methanohalophilus portucalensis FDF-1
• タンパク質・核酸の鎖数: 1
• 化学式量合計: 33139.61

構造登録者

Lee, Y.R.,Lin, T.S.,Lai, S.J.,Liu, M.S.,Lai, M.C.,Chan, N.L. (登録日: 2016-10-02, 公開日: 2016-11-23, 最終更新日: 2023-11-15)

主引用文献

Lee, Y.R.,Lin, T.S.,Lai, S.J.,Liu, M.S.,Lai, M.C.,Chan, N.L.
Structural Analysis of Glycine Sarcosine N-methyltransferase from Methanohalophilus portucalensis Reveals Mechanistic Insights into the Regulation of Methyltransferase Activity.
Sci Rep, 6:38071-38071, 2016

PubMed Abstract: Methyltransferases play crucial roles in many cellular processes, and various regulatory mechanisms have evolved to control their activities. For methyltransferases involved in biosynthetic pathways, regulation via feedback inhibition is a commonly employed strategy to prevent excessive accumulation of the pathways' end products. To date, no biosynthetic methyltransferases have been characterized by X-ray crystallography in complex with their corresponding end product. Here, we report the crystal structures of the glycine sarcosine N-methyltransferase from the halophilic archaeon Methanohalophilus portucalensis (MpGSMT), which represents the first structural elucidation of the GSMT methyltransferase family. As the first enzyme in the biosynthetic pathway of the osmoprotectant betaine, MpGSMT catalyzes N-methylation of glycine and sarcosine, and its activity is feedback-inhibited by the end product betaine. A structural analysis revealed that, despite the simultaneous presence of both substrate (sarcosine) and cofactor (S-adenosyl-L-homocysteine; SAH), the enzyme was likely crystallized in an inactive conformation, as additional structural changes are required to complete the active site assembly. Consistent with this interpretation, the bound SAH can be replaced by the methyl donor S-adenosyl-L-methionine without triggering the methylation reaction. Furthermore, the observed conformational state was found to harbor a betaine-binding site, suggesting that betaine may inhibit MpGSMT activity by trapping the enzyme in an inactive form. This work implicates a structural basis by which feedback inhibition of biosynthetic methyltransferases may be achieved.

PubMed: 27934872
DOI: 10.1038/srep38071

実験手法

X-RAY DIFFRACTION (1.776 Å)