1PQP

Crystal Structure of the C136S Mutant of Aspartate Semialdehyde Dehydrogenase from Haemophilus influenzae Bound with Aspartate Semialdehyde and Phosphate

Summary for 1PQP

• Entry DOI: 10.2210/pdb1pqp/pdb
• Related: 1NWC 1NWH 1NX6
• Descriptor: Aspartate-semialdehyde dehydrogenase, PHOSPHATE ION, L-HOMOSERINE, ... (4 entities in total)
• Functional Keywords: enzyme, l-aspartate semialdehyde, l-aspartate semialdehyde dehydrogenase, phosphate, oxidoreductase
• Biological source: Haemophilus influenzae Rd
• Total number of polymer chains: 1
• Total formula weight: 40781.76

Authors

Blanco, J.,Moore, R.A.,Faehnle, C.R.,Viola, R.E. (deposition date: 2003-06-18, release date: 2004-08-10, Last modification date: 2025-11-12)

Primary citation

Blanco, J.,Moore, R.A.,Faehnle, C.R.,Viola, R.E.
Critical catalytic functional groups in the mechanism of aspartate-beta-semialdehyde dehydrogenase.
Acta Crystallogr.,Sect.D, 60:1808-1815, 2004

PubMed Abstract: Aspartate-beta-semialdehyde dehydrogenase (ASADH) catalyzes the reductive dephosphorylation of beta-aspartyl phosphate to L-aspartate-beta-semialdehyde in the aspartate biosynthetic pathway. This pathway is not found in humans or other eukaryotic organisms, yet is required for the production of threonine, isoleucine, methionine and lysine in most microorganisms. The mechanism of this enzyme has been examined through the structures of two active-site mutants of ASADH from Haemophilus influenzae. Replacement of the enzyme active-site cysteine with serine (C136S) leads to a dramatic loss of catalytic activity caused by the expected decrease in nucleophilicity, but also by a change in the orientation of the serine hydroxyl group relative to the cysteine thiolate. In contrast, in the H277N active-site mutant the introduced amide is oriented in virtually the same position as that of the histidine imidazole ring. However, a shift in the position of the bound reaction intermediate to accommodate this shorter asparagine side chain, coupled with the inability of this introduced amide to serve as a proton acceptor, results in a 100-fold decrease in the catalytic efficiency of H277N relative to the native enzyme. These mutant enzymes have the same overall fold and high structural identity to native ASADH. However, small perturbations in the positioning of essential catalytic groups or reactive intermediates have dramatic effects on catalytic efficiency.

PubMed: 15388927
DOI: 10.1107/S0907444904020104

Experimental method

X-RAY DIFFRACTION (2.06 Å)