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New page: left|200px<br /><applet load="1cla" size="450" color="white" frame="true" align="right" spinBox="true" caption="1cla, resolution 2.34Å" /> '''EVIDENCE FOR TRANSIT...
 
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[[Image:1cla.jpg|left|200px]]<br /><applet load="1cla" size="450" color="white" frame="true" align="right" spinBox="true"
caption="1cla, resolution 2.34&Aring;" />
'''EVIDENCE FOR TRANSITION-STATE STABILIZATION BY SERINE-148 IN THE CATALYTIC MECHANISM OF CHLORAMPHENICOL ACETYLTRANSFERASE'''<br />


==Overview==
==EVIDENCE FOR TRANSITION-STATE STABILIZATION BY SERINE-148 IN THE CATALYTIC MECHANISM OF CHLORAMPHENICOL ACETYLTRANSFERASE==
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 Modeling studies, (P. C. E. Moody and A. G. W. Leslie, unpublished results) suggested that, the hydroxyl group of Ser-148 could be involved in transition-state, stabilization via a hydrogen bond to the oxyanion of the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).
<StructureSection load='1cla' size='340' side='right'caption='[[1cla]], [[Resolution|resolution]] 2.34&Aring;' scene=''>
== Structural highlights ==
<table><tr><td colspan='2'>[[1cla]] is a 1 chain structure with sequence from [https://en.wikipedia.org/wiki/Escherichia_coli Escherichia coli]. 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='method'><td class="sblockLbl"><b>[[Empirical_models|Method:]]</b></td><td class="sblockDat" id="methodDat">X-ray diffraction, [[Resolution|Resolution]] 2.34&#8491;</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='resources'><td class="sblockLbl"><b>Resources:</b></td><td class="sblockDat"><span class='plainlinks'>[https://proteopedia.org/fgij/fg.htm?mol=1cla FirstGlance], [http://oca.weizmann.ac.il/oca-bin/ocaids?id=1cla OCA], [https://pdbe.org/1cla PDBe], [https://www.rcsb.org/pdb/explore.do?structureId=1cla RCSB], [https://www.ebi.ac.uk/pdbsum/1cla PDBsum], [https://prosat.h-its.org/prosat/prosatexe?pdbcode=1cla ProSAT]</span></td></tr>
</table>
== Function ==
[https://www.uniprot.org/uniprot/CAT3_ECOLX CAT3_ECOLX] This enzyme is an effector of chloramphenicol resistance in bacteria.
== Evolutionary Conservation ==
[[Image:Consurf_key_small.gif|200px|right]]
Check<jmol>
  <jmolCheckbox>
    <scriptWhenChecked>; select protein; define ~consurf_to_do selected; consurf_initial_scene = true; script "/wiki/ConSurf/cl/1cla_consurf.spt"</scriptWhenChecked>
    <scriptWhenUnchecked>script /wiki/extensions/Proteopedia/spt/initialview01.spt</scriptWhenUnchecked>
    <text>to colour the structure by Evolutionary Conservation</text>
  </jmolCheckbox>
</jmol>, as determined by [http://consurfdb.tau.ac.il/ ConSurfDB]. You may read the [[Conservation%2C_Evolutionary|explanation]] of the method and the full data available from [http://bental.tau.ac.il/new_ConSurfDB/main_output.php?pdb_ID=1cla ConSurf].
<div style="clear:both"></div>


==About this Structure==
==See Also==
1CLA is a [http://en.wikipedia.org/wiki/Single_protein Single protein] structure of sequence from [http://en.wikipedia.org/wiki/Escherichia_coli Escherichia coli] with CO and CLM as [http://en.wikipedia.org/wiki/ligands ligands]. Active as [http://en.wikipedia.org/wiki/Chloramphenicol_O-acetyltransferase Chloramphenicol O-acetyltransferase], with EC number [http://www.brenda-enzymes.info/php/result_flat.php4?ecno=2.3.1.28 2.3.1.28] Full crystallographic information is available from [http://ispc.weizmann.ac.il/oca-bin/ocashort?id=1CLA OCA].
*[[Chloramphenicol acetyltransferase 3D structures|Chloramphenicol acetyltransferase 3D structures]]
 
__TOC__
==Reference==
</StructureSection>
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:[http://ispc.weizmann.ac.il//pmbin/getpm?pmid=2109633 2109633]
[[Category: Chloramphenicol O-acetyltransferase]]
[[Category: Escherichia coli]]
[[Category: Escherichia coli]]
[[Category: Single protein]]
[[Category: Large Structures]]
[[Category: Gibbs, M.R.]]
[[Category: Gibbs MR]]
[[Category: Leslie, A.G.W.]]
[[Category: Leslie AGW]]
[[Category: CLM]]
[[Category: CO]]
[[Category: transferase (acyltransferase)]]
 
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Retrieved from "https://proteopedia.org/1cla"