 |
PDBsum entry 1bqa
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
 |
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
Aminotransferase
|
PDB id
|
|
|
|
1bqa
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
 |
Contents |
 |
|
|
|
|
|
|
|
|
|
|
* Residue conservation analysis
|
|
|
|
|
References listed in PDB file
|
|
|
Key reference
|
|
|
Title
|
|
Functional and structural analysis of cis-Proline mutants of escherichia coli aspartate aminotransferase.
|
|
|
Authors
|
|
L.Birolo,
V.N.Malashkevich,
G.Capitani,
F.De luca,
A.Moretta,
J.N.Jansonius,
G.Marino.
|
|
|
Ref.
|
|
Biochemistry, 1999,
38,
905-913.
[DOI no: ]
|
|
|
PubMed id
|
|
|
|
|
|
Abstract
|
|
|
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.
|
|
|
|
|
|
|
