1cla

<table><tr><td colspan='2'>[[1cla]] is a 1 chain structure. Full crystallographic information is available from [http://oca.weizmann.ac.il/oca-bin/ocashort?id=1CLA OCA]. For a <b>guided tour on the structure components</b> use [https://proteopedia.org/fgij/fg.htm?mol=1CLA FirstGlance]. <br>

</td></tr><tr id='ligand'><td class="sblockLbl"><b>[[Ligand|Ligands:]]</b></td><td class="sblockDat" id="ligandDat"><scene name='pdbligand=CLM:CHLORAMPHENICOL'>CLM</scene>, <scene name='pdbligand=CO:COBALT+(II)+ION'>CO</scene></td></tr>

<tr id='activity'><td class="sblockLbl"><b>Activity:</b></td><td class="sblockDat"><span class='plainlinks'>[https://en.wikipedia.org/wiki/Chloramphenicol_O-acetyltransferase Chloramphenicol O-acetyltransferase], with EC number [https://www.brenda-enzymes.info/php/result_flat.php4?ecno=2.3.1.28 2.3.1.28] </span></td></tr>

[[https://www.uniprot.org/uniprot/CAT3_ECOLX CAT3_ECOLX]] This enzyme is an effector of chloramphenicol resistance in bacteria.

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== Publication Abstract from PubMed ==

The function of conserved Ser-148 of chloramphenicol acetyltransferase (CAT) has been investigated by site-directed mutagenesis. Modeling studies (P. C. E. Moody and A. G. W. Leslie, unpublished results) suggested that the hydroxyl group of Ser-148 could be involved in transition-state stabilization via a hydrogen bond to the oxyanion of the putative tetrahedral intermediate. Replacement of serine by alanine results in a mutant enzyme (Ala-148 CAT) with kcat reduced 53-fold and only minor changes in Km values for chloramphenicol and acetyl-CoA. The Ser-148----Gly substitution gives rise to a mutant enzyme (Gly-148 CAT) with kcat reduced only 10-fold. A water molecule may partially replace the hydrogen-bonding potential of Ser-148 in Gly-148 CAT. The three-dimensional structure of Ala-148 CAT at 2.34-A resolution is isosteric with that of wild-type CAT with two exceptions: the absence of the Ser-148 hydroxyl group and the loss of one poorly ordered water molecule from the active site region. The results are consistent with a catalytic role for Ser-148 rather than a structural one and support the hypothesis that Ser-148 is involved in transition-state stabilization. Ser-148 has also been replaced with cysteine and asparagine; the Ser-148----Cys mutation results in a 705-fold decrease in kcat and the Ser-148----Asn substitution in a 214-fold reduction in kcat. Removing the hydrogen bond donor (Ser-148----Ala or Gly) is less deleterious than replacing Ser-148 with alternative possible hydrogen bond donors (Ser-148----Cys or Asn).

Evidence for transition-state stabilization by serine-148 in the catalytic mechanism of chloramphenicol acetyltransferase.,Lewendon A, Murray IA, Shaw WV, Gibbs MR, Leslie AG Biochemistry. 1990 Feb 27;29(8):2075-80. PMID:2109633<ref>PMID:2109633</ref>

From MEDLINE&reg;/PubMed&reg;, a database of the U.S. National Library of Medicine.<br>

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== References ==

<references/>

[[Category: Chloramphenicol O-acetyltransferase]]

[[Category: Gibbs, M R]]

[[Category: Leslie, A G.W]]