5HII
Crystal structure of glycine sarcosine N-methyltransferase (GSMT) from Methanohalophilus portucalensis (apo form)
Summary for 5HII
| Entry DOI | 10.2210/pdb5hii/pdb |
| Related | 5GWX 5H02 5HIJ 5HIK 5HIL 5HIM |
| Descriptor | Glycine sarcosine N-methyltransferase, 1,2-ETHANEDIOL (3 entities in total) |
| Functional Keywords | s-adenosylmethionine-dependent methyltransferases (sam or adomet-mtase), class i, monomethylation of glycine and sarcosine, rate-limiting enzyme in betaine biosynthesis, betaine-mediated feedback inhibition, transferase |
| Biological source | Methanohalophilus portucalensis FDF-1 |
| Total number of polymer chains | 1 |
| Total formula weight | 33172.70 |
| Authors | |
| Primary citation | 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 Cited by 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: 27934872DOI: 10.1038/srep38071 PDB entries with the same primary citation |
| Experimental method | X-RAY DIFFRACTION (1.9 Å) |
Structure validation
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