[Conformation of aspartate aminotransferase in crystals]. / Konformatsii aspartataminotransferazy v kristalle.

X-ray study of chicken cytosolic aspartate aminotransferase revealed conformational changes in the protein of two kinds: (1) a shift of the small domain adjacent to substrate-binding area due to interaction of the protein with two carboxyl groups of substrate and (2) a change in inclination of the coenzyme plane due to replacement of C = N bond of the coenzyme with Lys-258 by C = N bond with a substrate. An asymmetry in subunit behaviour is observed in both cases: the domain is shifted in one subunit and the coenzyme is rotated in other. Substrate-binding properties of each subunit are strictly dependent on the protein conformation in substrate-binding area.

Electron density map of chicken heart cytosol aspartate transaminase at 3.5 A resolution.

Aspartate transaminase (EC 2.6.1.1., Asp-transaminase) has been studied extensively, and much is now known about its physico-chemical, catalytic and other properties. X-ray studies that can provide a structural foundation for the events that occur during the transamination reaction are under way on three species of Asp-transaminase: the cytosolic enzyme from pig and chicken hearts, and the mitochondrial chicken heart enzyme. We describe here the interpretation of an electron density map of Asp-transaminase from chicken heart cytosol at 3.5 A.