1ssm: Difference between revisions

Revision as of 09:05, 3 May 2008

Serine Acetyltransferase- Apoenzyme (truncated)

OverviewOverview

Serine acetyltransferase (SAT, EC 2.3.1.30) catalyzes the CoA-dependent acetylation of the side chain hydroxyl group of l-serine to form O-acetylserine, as the first step of a two-step biosynthetic pathway in bacteria and plants leading to the formation of l-cysteine. This reaction represents a key metabolic point of regulation for the cysteine biosynthetic pathway due to its feedback inhibition by cysteine. We have determined the X-ray crystal structure of Haemophilus influenzae SAT in complexes with CoA and its cysteine feedback inhibitor. The enzyme is a 175 kDa hexamer displaying the characteristic left-handed parallel beta-helix (LbetaH) structural domain of the hexapeptide acyltransferase superfamily of enzymes. Cysteine is bound in a crevice between adjacent LbetaH domains and underneath a loop excluded from the coiled LbetaH. The proximity of its thiol group to the thiol group of CoA derived from superimposed models of the cysteine and CoA complexes confirms that cysteine is bound at the active site. Analysis of the contacts of SAT with cysteine and CoA and the conformational differences that distinguish these complexes provides a structural basis for cysteine feedback inhibition, which invokes competition between cysteine and serine binding and a cysteine-induced conformational change of the C-terminal segment of the enzyme that excludes binding of the cofactor.

About this StructureAbout this Structure

1SSM is a Single protein structure of sequence from Haemophilus influenzae. Full crystallographic information is available from OCA.

ReferenceReference

Structure of serine acetyltransferase in complexes with CoA and its cysteine feedback inhibitor., Olsen LR, Huang B, Vetting MW, Roderick SL, Biochemistry. 2004 May 25;43(20):6013-9. PMID:15147185 Page seeded by OCA on Sat May 3 09:05:45 2008

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OCA

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 [[Image:1ssm.gif|left|200px]]
- {{Structure
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-|LIGAND= <scene name='pdbligand=MSE:SELENOMETHIONINE'>MSE</scene>
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-|ACTIVITY= <span class='plainlinks'>[http://en.wikipedia.org/wiki/Serine_O-acetyltransferase Serine O-acetyltransferase], with EC number [http://www.brenda-enzymes.info/php/result_flat.php4?ecno=2.3.1.30 2.3.1.30] </span>
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-|GENE= CYSE, HI0606 ([http://www.ncbi.nlm.nih.gov/Taxonomy/Browser/wwwtax.cgi?mode=Info&srchmode=5&id=727 Haemophilus influenzae])
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-|DOMAIN=
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-|RELATEDENTRY=[[1ssq|1SSQ]], [[1sst|1SST]]
-|RESOURCES=<span class='plainlinks'>[http://oca.weizmann.ac.il/oca-docs/fgij/fg.htm?mol=1ssm FirstGlance], [http://oca.weizmann.ac.il/oca-bin/ocaids?id=1ssm OCA], [http://www.ebi.ac.uk/pdbsum/1ssm PDBsum], [http://www.rcsb.org/pdb/explore.do?structureId=1ssm RCSB]</span>
-}}
 '''Serine Acetyltransferase- Apoenzyme (truncated)'''
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 [[Category: Roderick, S L.]]
 [[Category: Vetting, M W.]]
-[[Category: left-handed parallel beta helix]]
+[[Category: Left-handed parallel beta helix]]
+''Page seeded by [http://oca.weizmann.ac.il/oca OCA ] on Sat May  3 09:05:45 2008''
-''Page seeded by [http://oca.weizmann.ac.il/oca OCA ] on Sun Mar 30 23:46:30 2008''