1m6e
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(New page: 200px<br /><applet load="1m6e" size="450" color="white" frame="true" align="right" spinBox="true" caption="1m6e, resolution 3.00Å" /> '''CRYSTAL STRUCTURE OF...)
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Revision as of 01:43, 25 November 2007
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CRYSTAL STRUCTURE OF SALICYLIC ACID CARBOXYL METHYLTRANSFERASE (SAMT)
Overview
Recently, a novel family of methyltransferases was identified in plants., Some members of this newly discovered and recently characterized, methyltransferase family catalyze the formation of small-molecule methyl, esters using S-adenosyl-L-Met (SAM) as a methyl donor and carboxylic, acid-bearing substrates as methyl acceptors. These enzymes include SAMT, (SAM:salicylic acid carboxyl methyltransferase), BAMT (SAM:benzoic acid, carboxyl methyltransferase), and JMT (SAM:jasmonic acid carboxyl, methyltransferase). Moreover, other members of this family of plant, methyltransferases have been found to catalyze the N-methylation of, caffeine precursors. The 3.0-A crystal structure of Clarkia breweri SAMT, in complex with the substrate salicylic acid and the demethylated product, S-adenosyl-L-homocysteine reveals a protein structure that possesses a, helical active site capping domain and a unique dimerization interface. In, addition, the chemical determinants responsible for the selection of, salicylic acid demonstrate the structural basis for facile variations of, substrate selectivity among functionally characterized plant, carboxyl-directed and nitrogen-directed methyltransferases and a growing, set of related proteins that have yet to be examined biochemically. Using, the three-dimensional structure of SAMT as a guide, we examined the, substrate specificity of SAMT by site-directed mutagenesis and activity, assays against 12 carboxyl-containing small molecules. Moreover, the, utility of structural information for the functional characterization of, this large family of plant methyltransferases was demonstrated by the, discovery of an Arabidopsis methyltransferase that is specific for the, carboxyl-bearing phytohormone indole-3-acetic acid.
About this Structure
1M6E is a Single protein structure of sequence from Clarkia breweri with LU, SAH and SAL as ligands. Full crystallographic information is available from OCA.
Reference
Structural basis for substrate recognition in the salicylic acid carboxyl methyltransferase family., Zubieta C, Ross JR, Koscheski P, Yang Y, Pichersky E, Noel JP, Plant Cell. 2003 Aug;15(8):1704-16. PMID:12897246
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