3aat: Difference between revisions

[[Image:3aat.gif|left|200px]]<br /><applet load="3aat" size="350" color="white" frame="true" align="right" spinBox="true"  

Arginine-386, the active-site residue of Escherichia coli aspartate aminotransferase (EC 2.6.1.1) that binds the substrate alpha-carboxylate, was replaced with tyrosine and phenylalanine by site-directed mutagenesis. This experiment was undertaken to elucidate the roles of particular enzyme-substrate interactions in triggering the substrate-induced conformational change in the enzyme. The activity and crystal structure of the resulting mutants were examined. The apparent second-order rate constants of both of these mutants are reduced by more than 5 orders of magnitude as compared to that of wild-type enzyme, though R386Y is slightly more active than R386F. The 2.5-A resolution structure of R386F in its native state was determined by using difference Fourier methods. The overall structure is very similar to that of the wild-type enzyme in the open conformation. The position of the Phe-386 side chain, however, appears to shift with respect to that of Arg-386 in the wild-type enzyme and to form new contacts with neighboring residues.

3AAT 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 <scene name='pdbligand=SO4:'>SO4</scene> and <scene name='pdbligand=PLP:'>PLP</scene> as [http://en.wikipedia.org/wiki/ligands ligands]. Active as [http://en.wikipedia.org/wiki/Aspartate_transaminase Aspartate transaminase], with EC number [http://www.brenda-enzymes.info/php/result_flat.php4?ecno=2.6.1.1 2.6.1.1] Full crystallographic information is available from [http://oca.weizmann.ac.il/oca-bin/ocashort?id=3AAT OCA].  

[[Category: Danishefsky, A T.]]

[[Category: Petsko, G A.]]

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