1OXO

ASPARTATE AMINOTRANSFERASE, H-ASP COMPLEX, OPEN CONFORMATION

Summary for 1OXO

• Entry DOI: 10.2210/pdb1oxo/pdb
• Descriptor: ASPARTATE AMINOTRANSFERASE, 4'-DEOXY-4'-ACETYLYAMINO-PYRIDOXAL-5'-PHOSPHATE (3 entities in total)
• Functional Keywords: vitamin b6, hydroxylamine derived inhibitors, aminotransferase
• Biological source: Gallus gallus (chicken)
• Cellular location: Mitochondrion matrix : P00508
• Total number of polymer chains: 2
• Total formula weight: 90629.38

Authors

Hohenester, E.,Schirmer, T.,Jansonius, J.N. (deposition date: 1995-12-23, release date: 1996-06-10, Last modification date: 2024-02-14)

Primary citation

Markovic-Housley, Z.,Schirmer, T.,Hohenester, E.,Khomutov, A.R.,Khomutov, R.M.,Karpeisky, M.Y.,Sandmeier, E.,Christen, P.,Jansonius, J.N.
Crystal structures and solution studies of oxime adducts of mitochondrial aspartate aminotransferase.
Eur.J.Biochem., 236:1025-1032, 1996

PubMed Abstract: The interaction of mitochondrial aspartate aminotransferase with hydroxylamine and five derivatives (in which the hydroxyl hydrogen is replaced by the side chain of naturally occurring amino acids) was investigated by X-ray diffraction as well as by kinetic and spectral measurements with the enzyme in solution. The inhibitors react with pyridoxal 5'-phosphate in the enzyme active site, both in solution and in the crystalline state, in a reversible single-step reaction forming spectrally distinct oxime adducts. Dissociation constants determined in solution range from 10(-8) M to 10(-6) M depending on the nature of the side-chain group. The crystal structures of the adducts of mitochondrial aspartate aminotransferase with the monocarboxylic analogue of L-aspartate in the open and closed enzyme conformation were determined at 0.23-nm and 0.25-nm resolution, respectively. This inhibitor binds to both the open and closed crystal forms of the enzyme without disturbing the crystalline order. Small differences in the conformation of the cofactor pyridoxal phosphate were detected between the omega-carboxylate of the inhibitor and Arg292 of the neighbouring subunit is mainly responsible for the attainment of near-coplanarity of the aldimine bond with the pyridine ring in the oxime adducts. Studies with a fluorescent probe aimed to detect shifts in the open/closed conformational equilibrium of the enzyme in oxime complexes showed that the hydroxylamine-derived inhibitors, even those containing a carboxylate group, do not induce the 'domain closure' in solution. This is probably due to the absence of the alpha-carboxylate group in the monocarboxylic hydroxylamine-derived inhibitors, emphasizing that both carboxylates of the substrates L-Asp and L-Glu are essential for stabilizing the closed form of aspartate aminotransferase.

PubMed: 8665890
DOI: 10.1111/j.1432-1033.1996.01025.x

Experimental method

X-RAY DIFFRACTION (2.3 Å)