MOLECULAR MODELING OF HUMAN RED-BLOOD-CELL PYRUVATE-KINASE - STRUCTURAL IMPLICATIONS OF A NOVEL G(1091) TO A-MUTATION CAUSING SEVERE NONSPHEROCYTIC HEMOLYTIC-ANEMIA

We present a novel G(1091) to A mutation in the human liver and red bl ood cell (RBC) pyruvate kinase (PK) gene causing severe hemolytic anem ia. In two families, three children were severely PK-deficient compoun d heterozygotes exhibiting the G(1091) to A mutation and a common G(15 29) to A mutation on the other allele. In one family, the mother, a G( 1091) to A heterozygote, later had a second baby with a new husband, a lso a G(1091) to A carrier. The baby was homozygous for the G(1091) to A mutation and died 6 weeks after birth from severe hemolysis. Bath m utant alleles were expressed at the RNA level. The G(1091) to A mutati on results in the substitution of a conserved glycine by an aspartate in domain A of RBC PK, whereas the G(1529) to A mutation leads to the substitution of a conserved arginine residue with glutamine in the C-d omain. Molecular modelling of human RBC PK, based on the crystal struc ture of cat muscle PK, shows that both mutations are located outside t he catalytic site at the interface of domains A and C. The mutations a re likely to disrupt the critical conformation of the interface by int roducing alternative salt bridges. In this way the GlY(364) to ASP and Arg(510) to Gln substitutions may cause PK deficiency by influencing the allosteric properties of the enzyme. (C) 1997 by The American Soci ety of Hematology.