Abstact

Crystal structures of phosphoglycerate kinase (PGK) from the psychrophile Pseudomonas sp. TACII 18 have been determined at high resolution by X-ray crystallography methods and compared with mesophilic, thermophilic and hyperthermophilic counterparts. PGK is a two-domain enzyme undergoing large domain movements to catalyze the production of ATP from 1,3-biphosphoglycerate and ADP. Whereas the conformational dynamics sustaining the catalytic mechanism of this hinge-bending enzyme now seems rather clear, the determinants which underlie high catalytic efficiency at low temperatures of this psychrophilic PGK were unknown. The comparison of the three-dimensional structures shows that multiple (global and local) specific adaptations have been brought about by this enzyme. Together, these reside in an overall increased flexibility of the cold-adapted PGK thereby allowing a better accessibility to the active site, but also a potentially more disordered transition state of the psychrophilic enzyme, due to the destabilization of some catalytic residues.