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1nbi

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{{STRUCTURE_1nbi| PDB=1nbi | SCENE= }}
{{STRUCTURE_1nbi| PDB=1nbi | SCENE= }}
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'''Structure of R175K mutated glycine N-methyltransferase complexed with S-adenosylmethionine, R175K:SAM.'''
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===Structure of R175K mutated glycine N-methyltransferase complexed with S-adenosylmethionine, R175K:SAM.===
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==Overview==
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Methyltransfer reactions are some of the most important reactions in biological systems. Glycine N-methyltransferase (GNMT) catalyzes the S-adenosyl-l-methionine- (SAM-) dependent methylation of glycine to form sarcosine. Unlike most SAM-dependent methyltransferases, GNMT has a relatively high value and is weakly inhibited by the product S-adenosyl-l-homocysteine (SAH). The major role of GNMT is believed to be the regulation of the cellular SAM/SAH ratio, which is thought to play a key role in SAM-dependent methyltransfer reactions. Crystal structures of GNMT complexed with SAM and acetate (a potent competitive inhibitor of Gly) and the R175K mutated enzyme complexed with SAM were determined at 2.8 and 3.0 A resolutions, respectively. With these crystal structures and the previously determined structures of substrate-free enzyme, a catalytic mechanism has been proposed. Structural changes occur in the transitions from the substrate-free to the binary complex and from the binary to the ternary complex. In the ternary complex stage, an alpha-helix in the N-terminus undergoes a major conformational change. As a result, the bound SAM is firmly connected to protein and a "Gly pocket" is created near the bound SAM. The second substrate Gly binds to Arg175 and is brought into the Gly pocket. Five hydrogen bonds connect the Gly in the proximity of the bound SAM and orient the lone pair orbital on the amino nitrogen (N) of Gly toward the donor methyl group (C(E)) of SAM. Thermal motion of the enzyme leads to a collision of the N and C(E) so that a S(N)2 methyltransfer reaction occurs. The proposed mechanism is supported by mutagenesis studies.
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(as it appears on PubMed at http://www.pubmed.gov), where 12859184 is the PubMed ID number.
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{{ABSTRACT_PUBMED_12859184}}
==About this Structure==
==About this Structure==
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[[Category: Glycine n-methyltransferase]]
[[Category: Glycine n-methyltransferase]]
[[Category: Methyltransferase]]
[[Category: Methyltransferase]]
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''Page seeded by [http://oca.weizmann.ac.il/oca OCA ] on Sat May 3 02:20:16 2008''
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''Page seeded by [http://oca.weizmann.ac.il/oca OCA ] on Sun Jul 27 17:19:18 2008''

Revision as of 14:19, 27 July 2008

Image:1nbi.png

Template:STRUCTURE 1nbi

Structure of R175K mutated glycine N-methyltransferase complexed with S-adenosylmethionine, R175K:SAM.

Template:ABSTRACT PUBMED 12859184

About this Structure

1NBI is a Single protein structure of sequence from Rattus norvegicus. Full crystallographic information is available from OCA.

Reference

Catalytic mechanism of glycine N-methyltransferase., Takata Y, Huang Y, Komoto J, Yamada T, Konishi K, Ogawa H, Gomi T, Fujioka M, Takusagawa F, Biochemistry. 2003 Jul 22;42(28):8394-402. PMID:12859184

Page seeded by OCA on Sun Jul 27 17:19:18 2008

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