STRUCTURAL AND FUNCTIONAL-PROPERTIES OF MUTANT ARG203PRO FROM YEAST PHOSPHOGLYCERATE KINASE, AS A MODEL OF PHOSPHOGLYCERATE KINASE-UPPSALA

A pathological variant of human phosphoglycerate kinase, phosphoglycer ate kinase-Uppsala, associated with chronic nonspherocytic hemolytic a nemia has been found to differ from the normal enzyme by substitution of an arginine at position 206 (corresponding to position 203 in yeast ) by a proline. In order to understand the structural and functional c onsequences of this mutation, the corresponding mutant in yeast phosph oglycerate kinase was constructed, The three-dimensional structure of this mutant was resolved at 2.9 Angstrom, Although the overall structu re is not modified, small local changes were observed, The kinetic par ameters of the mutant were not found to be greatly affected, the catal ytic constant being lowered by only 10-20%. The most significant diffe rence when compared with the wild-type enzyme is a decrease in stabili ty by about 3 kcal/mol, The physiological implications of this instabi lity are discussed.