2QB3

Structural Studies Reveal the Inactivation of E. coli L-Aspartate Aminotransferase by (s)-4,5-dihydro-2-thiophenecarboxylic acid (SADTA) via Two Mechanisms (at pH 7.5)

Summary for 2QB3

• Entry DOI: 10.2210/pdb2qb3/pdb
• Related: 2Q7W 2QA3 2QB2
• Descriptor: Aspartate aminotransferase, SULFATE ION, 4-[({3-HYDROXY-2-METHYL-5-[(PHOSPHONOOXY)METHYL]PYRIDIN-4-YL}METHYL)AMINO]THIOPHENE-2-CARBOXYLIC ACID, ... (6 entities in total)
• Functional Keywords: mechanism-based inactivator, ph dependence, aspartate aminotransferase, sadta, plp, transferase
• Biological source: Escherichia coli
• Cellular location: Cytoplasm: P00509
• Total number of polymer chains: 1
• Total formula weight: 45203.60

Authors

Liu, D.,Pozharski, E.,Lepore, B.,Fu, M.,Silverman, R.B.,Petsko, G.A.,Ringe, D. (deposition date: 2007-06-15, release date: 2007-12-04, Last modification date: 2011-07-13)

Primary citation

Liu, D.,Pozharski, E.,Lepore, B.W.,Fu, M.,Silverman, R.B.,Petsko, G.A.,Ringe, D.
Inactivation of Escherichia coli L-aspartate aminotransferase by (S)-4-amino-4,5-dihydro-2-thiophenecarboxylic acid reveals "a tale of two mechanisms".
Biochemistry, 46:10517-10527, 2007

PubMed Abstract: As a mechanism-based inactivator of PLP-enzymes, (S)-4-amino-4,5-dihydro-2-thiophenecarboxylic acid (SADTA) was cocrystallized with Escherichia coli aspartate aminotransferase (l-AspAT) at a series of pH values ranging from 6 to 8. Five structural models with high resolution (1.4-1.85 A) were obtained for l-AspAT-SADTA complexes at pH 6.0, 6.5, 7.0, 7.5, and 8.0. Electron densities of the models showed that two different adducts had formed in the active sites. One adduct was formed from SADTA covalently linked to pyridoxal 5'-phosphate (PLP) while the other adduct was formed with the inhibitor covalently linked to Lysine246,1 the active site lysine. Moreover, there is a strong indication based on the electron densities that the occurrence of the two adducts is pH dependent. We conclude that SADTA inactivates l-AspAT via two different mechanisms based on the binding direction of the inactivator. Additionally, the structural models also show pH dependence of the protein structure itself, which provided detailed mechanistic implications for l-AspAT.

PubMed: 17713924
DOI: 10.1021/bi700663n

Experimental method

X-RAY DIFFRACTION (1.45 Å)