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4cla

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[[Image:4cla.gif|left|200px]]
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{{STRUCTURE_4cla| PDB=4cla | SCENE= }}
{{STRUCTURE_4cla| PDB=4cla | SCENE= }}
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'''ALTERNATIVE BINDING MODES FOR CHLORAMPHENICOL AND 1-SUBSTITUTED CHLORAMPHENICOL ANALOGUES REVEALED BY SITE-DIRECTED MUTAGENESIS AND X-RAY CRYSTALLOGRAPHY OF CHLORAMPHENICOL ACETYLTRANSFERASE'''
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===ALTERNATIVE BINDING MODES FOR CHLORAMPHENICOL AND 1-SUBSTITUTED CHLORAMPHENICOL ANALOGUES REVEALED BY SITE-DIRECTED MUTAGENESIS AND X-RAY CRYSTALLOGRAPHY OF CHLORAMPHENICOL ACETYLTRANSFERASE===
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==Overview==
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Leucine-160 of chloramphenicol acetyltransferase (CAT) has been replaced by site-directed mutagenesis to investigate enzyme-ligand interactions at the 1-hydroxyl substituent of the substrate chloramphenicol. The consequences of the substitution of Leu-160 by glutamine and by phenylalanine were deduced from the steady-state kinetic parameters for acetyl transfer from acetyl-CoA to the 3-hydroxyl of chloramphenicol and its analogues 1-deoxychloramphenicol and 1-acetylchloramphenicol. The acetyl group of the latter, which is a substrate both in vivo and in vitro, could potentially bind in a similar position to the 1-hydroxyl of chloramphenicol, in close proximity to the side chain of Leu-160. In the case of Gln-160 CAT, large increases in Km for the three acetyl acceptors were accompanied by small decreases in kcat and in apparent affinity for acetyl-CoA. Such results are consistent with the introduction of the relatively hydrophilic amide in place of the delta-methyl groups of Leu-160. The kinetic properties of Phe-160 CAT were unexpected in that Km for each of the three acetyl acceptors was unchanged or reduced, compared to the equivalent parameters for the wild-type enzyme, whereas kcat fell significantly (44-83-fold) in each case. The ratios of specificity constants (kcat/Km) for the acetylation of chloramphenicol compared with the alternative acyl acceptors were similar for wild-type and mutant enzymes. As the residue substitutions for Leu-160 do not result in enhanced discrimination against the binding and acetylation of 1-acetylchloramphenicol, it appears unlikely that the 1-acetyl group binds to the CAT active site in the same position as that occupied by the 1-hydroxyl of chloramphenicol.(ABSTRACT TRUNCATED AT 250 WORDS)
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{{ABSTRACT_PUBMED_2015231}}
==About this Structure==
==About this Structure==
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[[Category: Single protein]]
[[Category: Single protein]]
[[Category: Leslie, A G.W.]]
[[Category: Leslie, A G.W.]]
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Revision as of 10:32, 3 July 2008

Image:4cla.png

Template:STRUCTURE 4cla

ALTERNATIVE BINDING MODES FOR CHLORAMPHENICOL AND 1-SUBSTITUTED CHLORAMPHENICOL ANALOGUES REVEALED BY SITE-DIRECTED MUTAGENESIS AND X-RAY CRYSTALLOGRAPHY OF CHLORAMPHENICOL ACETYLTRANSFERASE

Template:ABSTRACT PUBMED 2015231

About this Structure

4CLA is a Single protein structure of sequence from Escherichia coli. Full crystallographic information is available from OCA.

Reference

Alternative binding modes for chloramphenicol and 1-substituted chloramphenicol analogues revealed by site-directed mutagenesis and X-ray crystallography of chloramphenicol acetyltransferase., Murray IA, Lewendon A, Williams JA, Cullis PM, Shaw WV, Leslie AG, Biochemistry. 1991 Apr 16;30(15):3763-70. PMID:2015231

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