1. Strain relief at the active site of phosphoserine aminotransferase induced by radiation damage.
- Author
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Dubnovitsky, Anatoly P., Ravelli, Raimond B.G., Popov, Alexander N., and Papageorgiou, Anastassios C.
- Abstract
The X-ray susceptibility of the lysine-pyridoxal-5′-phosphate Schiff base in Bacillus alcalophilus phosphoserine aminotransferase has been investigated using crystallographic data collected at 100 K to 1.3 Å resolution, complemented by on-line spectroscopic studies. X-rays induce deprotonation of the internal aldimine, changes in the Schiff base conformation, displacement of the cofactor molecule, and disruption of the Schiff base linkage between pyridoxal-5′-phosphate and the Lys residue. Analysis of the 'undamaged' structure reveals a significant chemical strain on the internal aldimine bond that leads to a pronounced geometrical distortion of the cofactor. However, upon crystal exposure to the X-rays, the strain and distortion are relaxed and eventually diminished when the total absorbed dose has exceeded 4.7 × 10
6 Gγ. Our data provide new insights into the enzymatic activation of pyridoxal-5′-phosphate and suggest that special care should be taken while using macromolecular crystallography to study details in strained active sites. [ABSTRACT FROM AUTHOR]- Published
- 2005
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