1bqd: Difference between revisions

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[[Image:1bqd.jpg|left|200px]]
{{Seed}}
[[Image:1bqd.png|left|200px]]


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{{STRUCTURE_1bqd|  PDB=1bqd  |  SCENE=  }}  
{{STRUCTURE_1bqd|  PDB=1bqd  |  SCENE=  }}  


'''ASPARTATE AMINOTRANSFERASE P138A/P195A DOUBLE MUTANT'''
===ASPARTATE AMINOTRANSFERASE P138A/P195A DOUBLE MUTANT===




==Overview==
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To elucidate the role of the two conserved cis-proline residues of aspartate aminotransferase (AspAT), one double and two single mutants of the enzyme from Escherichia coli (EcAspAT) were prepared: P138A, P195A and P138A/P195A in which the two prolines were replaced by alanine. The crystal structures of P195A and P138A/P195A have been determined at 2.3-2.1 A resolution. The wild-type geometry, including the cis conformation of the 194-195 peptide bond is retained upon substitution of proline 195 by alanine, whereas the trans conformation is adopted at the 137-138 peptide bond. Quite surprisingly, the replacement of each of the two prolines by alanine does not significantly affect either the activity or the stability of the protein. All the three mutants follow the same pathway as the wild type for unfolding equilibrium induced by guanidine hydrochloride [Herold, M., and Kirschner, K. (1990) Biochemistry 29, 1907-1913]. The kinetics of renaturation of P195A, where the alanine retains the wild-type cis conformation, is faster than wild type, whereas renaturation of P138A, which adopts the trans conformation, is slower. We conclude that cis-prolines seem to have been retained throughout the evolution of aspartate aminotransferase to possibly play a subtle role in directing the traffic of intermediates toward the unique structure of the native state, rather than to respond to the needs for a specific catalytic or functional role.
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{{ABSTRACT_PUBMED_9893985}}


==About this Structure==
==About this Structure==
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[[Category: Aminotransferase]]
[[Category: Aminotransferase]]
[[Category: Transferase]]
[[Category: Transferase]]
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''Page seeded by [http://oca.weizmann.ac.il/oca OCA ] on Mon Jun 30 19:31:54 2008''

Revision as of 16:31, 30 June 2008

File:1bqd.png

Template:STRUCTURE 1bqd

ASPARTATE AMINOTRANSFERASE P138A/P195A DOUBLE MUTANT

Template:ABSTRACT PUBMED 9893985

About this Structure

1BQD is a Single protein structure of sequence from Escherichia coli. Full crystallographic information is available from OCA.

Reference

Functional and structural analysis of cis-proline mutants of Escherichia coli aspartate aminotransferase., Birolo L, Malashkevich VN, Capitani G, De Luca F, Moretta A, Jansonius JN, Marino G, Biochemistry. 1999 Jan 19;38(3):905-13. PMID:9893985

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