2c7y: Difference between revisions

[[Image:2c7y.gif|left|200px]]<br /><applet load="2c7y" size="350" color="white" frame="true" align="right" spinBox="true"  

Crystal structures of peroxisomal Arabidopsis thaliana 3-ketoacyl-CoA thiolase (AtKAT), an enzyme of fatty acid beta-oxidation, are reported. The subunit, a typical thiolase, is a combination of two similar alpha/beta domains capped with a loop domain. The comparison of AtKAT with the Saccharomyces cerevisiae homologue (ScKAT) structure reveals a different placement of subunits within the functional dimers and that a polypeptide segment forming an extended loop around the open catalytic pocket of ScKAT converts to alpha-helix in AtKAT, and occludes the active site. A disulfide is formed between Cys192, on this helix, and Cys138, a catalytic residue. Access to Cys138 is determined by the structure of this polypeptide segment. AtKAT represents an oxidized, previously unknown inactive form, whilst ScKAT is the reduced and active enzyme. A high level of sequence conservation is observed, including Cys192, in eukaryotic peroxisomal, but not mitochondrial or prokaryotic KAT sequences, for this labile loop/helix segment. This indicates that KAT activity in peroxisomes is influenced by a disulfide/dithiol change linking fatty acid beta-oxidation with redox regulation.

2C7Y is a [http://en.wikipedia.org/wiki/Single_protein Single protein] structure of sequence from [http://en.wikipedia.org/wiki/Arabidopsis_thaliana Arabidopsis thaliana]. Active as [http://en.wikipedia.org/wiki/Acetyl-CoA_C-acyltransferase Acetyl-CoA C-acyltransferase], with EC number [http://www.brenda-enzymes.info/php/result_flat.php4?ecno=2.3.1.16 2.3.1.16] Full crystallographic information is available from [http://oca.weizmann.ac.il/oca-bin/ocashort?id=2C7Y OCA].  

[[Category: Alphey, M S.]]

[[Category: Bryce, J H.]]

[[Category: Hunter, W N.]]

[[Category: Leonard, G A.]]

[[Category: Smith, S M.]]

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