4pgh: Difference between revisions
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''' | ==Caffeic acid O-methyltransferase from Sorghum bicolor== | ||
<StructureSection load='4pgh' size='340' side='right' caption='[[4pgh]], [[Resolution|resolution]] 2.80Å' scene=''> | |||
== Structural highlights == | |||
<table><tr><td colspan='2'>[[4pgh]] is a 4 chain structure. Full crystallographic information is available from [http://oca.weizmann.ac.il/oca-bin/ocashort?id=4PGH OCA]. For a <b>guided tour on the structure components</b> use [http://oca.weizmann.ac.il/oca-docs/fgij/fg.htm?mol=4PGH FirstGlance]. <br> | |||
</td></tr><tr><td class="sblockLbl"><b>[[Ligand|Ligands:]]</b></td><td class="sblockDat"><scene name='pdbligand=SAM:S-ADENOSYLMETHIONINE'>SAM</scene><br> | |||
<tr><td class="sblockLbl"><b>[[Related_structure|Related:]]</b></td><td class="sblockDat">[[4pgg|4pgg]]</td></tr> | |||
<tr><td class="sblockLbl"><b>Activity:</b></td><td class="sblockDat"><span class='plainlinks'>[http://en.wikipedia.org/wiki/Caffeate_O-methyltransferase Caffeate O-methyltransferase], with EC number [http://www.brenda-enzymes.info/php/result_flat.php4?ecno=2.1.1.68 2.1.1.68] </span></td></tr> | |||
<tr><td class="sblockLbl"><b>Resources:</b></td><td class="sblockDat"><span class='plainlinks'>[http://oca.weizmann.ac.il/oca-docs/fgij/fg.htm?mol=4pgh FirstGlance], [http://oca.weizmann.ac.il/oca-bin/ocaids?id=4pgh OCA], [http://www.rcsb.org/pdb/explore.do?structureId=4pgh RCSB], [http://www.ebi.ac.uk/pdbsum/4pgh PDBsum]</span></td></tr> | |||
<table> | |||
<div style="background-color:#fffaf0;"> | |||
== Publication Abstract from PubMed == | |||
Using S-adenosylmethionine as the methyl donor, caffeic acid O-methyltransferase from Sorghum bicolor (SbCOMT) methylates the 5-hydroxyl group of its preferred substrate, 5-hydroxyconiferaldehyde. In order to determine the mechanism of SbCOMT and understand the observed reduction in the lignin syringyl-to-guaiacyl ratio of three brown midrib12 (bmr12) mutants that carry COMT gene missense mutations, we determined the apo-form and S-adenosylmethionine-binary complex SbCOMT crystal structures, and established the ternary complex structure with 5-hydroxyconiferaldehyde by molecular modeling. These structures revealed many features shared with monocot ryegrass (Lolium perenne) and dicot alfalfa (Medicago sativa) COMTs. SbCOMT steady-state kinetic and calorimetric data suggest a random bi-bi mechanism. Based on our structural, kinetic and thermodynamic results, we propose that the observed reactivity hierarchy among 4,5-dihydroxy-3-methoxycinnamyl (and 3,4-dihydroxycinnamyl) aldehyde, alcohol and acid substrates arises from the ability of the aldehyde to stabilize the anionic intermediate that results from deprotonation of the 5-hydroxyl group by His267. Additionally, despite the presence of other phenylpropanoid substrates in vivo, sinapaldehyde is the preferential product, as demonstrated by its low Km for 5-hydroxyconiferaldehyde. Unlike its acid and alcohol substrates, the aldehydes exhibit product inhibition and we propose this is due to non-productive binding of the s-cis-form of the aldehydes inhibiting productive binding of the s-trans-form. The s-cis-aldehydes most likely act only as inhibitors because the high rotational energy barrier around the 2-propenyl bond prevents s-trans conversion, unlike alcohol substrates whose low 2-propenyl bond rotational energy barrier enables rapid s-cis/s-trans interconversion. | |||
Determination of the structure and catalytic mechanism of Sorghum bicolor caffeic acid O-methyltransferase and the structural impact of three brown midrib12 mutations.,Green AR, Lewis KM, Barr JT, Jones JP, Lu F, Ralph J, Vermerris W, Sattler SE, Kang C Plant Physiol. 2014 Jun 19. pii: pp.114.241729. PMID:24948836<ref>PMID:24948836</ref> | |||
From MEDLINE®/PubMed®, a database of the U.S. National Library of Medicine.<br> | |||
</div> | |||
== References == | |||
<references/> | |||
__TOC__ | |||
</StructureSection> | |||
[[Category: Caffeate O-methyltransferase]] | |||
[[Category: Green, A R.]] | |||
[[Category: Kang, C.]] | |||
[[Category: Lewis, K M.]] | |||
[[Category: Sam-dependent o-methyltransferase]] | |||
