7tln: Difference between revisions

[[Image:7tln.gif|left|200px]]<br /><applet load="7tln" size="350" color="white" frame="true" align="right" spinBox="true"  

The mode of binding of the irreversible thermolysin inhibitor ClCH2CO-DL-(N-OH)Leu-OCH3 [Rasnick, D., &amp; Powers, J.C. (1978) Biochemistry 17, 4363-4369] has been determined by X-ray crystallography at a resolution of 2.3 A and the structure of the covalent complex refined to give a crystallographic residual of 17.0%. This is the first such structural study of an active-site-directed covalent complex of a zinc protease. As anticipated by Rasnick and Powers, the inhibitor alkylates Glu-143 in the thermolysin active site, and the hydroxamic acid moiety coordinates the zinc ion. The formation of the covalent complex is associated with a significant shift in a segment of the polypeptide backbone in the vicinity of the active site. This conformational adjustment appears to be necessary to relieve steric hindrance which would otherwise prevent alkylation of Glu-143. It is suggested that this steric hindrance, which occurs for thermolysin but would not be expected for carboxypeptidase A, accounts for the previously inexplicable difference in reactivity of these two metalloproteases toward N-haloacetyl amino acids. The relevance of this steric hindrance to the mechanism of catalysis is discussed. In agreement with previous results [Kester, W. R., &amp; Matthews, B. W. (1977) Biochemistry 16, 2506-2516], it appears that steric hindrance prevents the direct attack of Glu-143 on the carbonyl carbon of an extended substrate, therefore ruling out the anhydride pathway in thermolysin-catalyzed hydrolysis of polypeptide substrates and their ester analogues.

7TLN is a [http://en.wikipedia.org/wiki/Single_protein Single protein] structure of sequence from [http://en.wikipedia.org/wiki/Bacillus_thermoproteolyticus Bacillus thermoproteolyticus] with <scene name='pdbligand=CA:'>CA</scene>, <scene name='pdbligand=ZN:'>ZN</scene> and <scene name='pdbligand=INC:'>INC</scene> as [http://en.wikipedia.org/wiki/ligands ligands]. This structure supersedes the now removed PDB entry 6TLN. Active as [http://en.wikipedia.org/wiki/Thermolysin Thermolysin], with EC number [http://www.brenda-enzymes.info/php/result_flat.php4?ecno=3.4.24.27 3.4.24.27] Full crystallographic information is available from [http://oca.weizmann.ac.il/oca-bin/ocashort?id=7TLN OCA].  

[[Category: Holmes, M A.]]

[[Category: Matthews, B W.]]

[[Category: Tronrud, D E.]]

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