Dissection of the functional domains of the sarcoplasmic reticulum Ca(2+)-ATPase by site-directed mutagenesis.

The results of site-directed mutagenesis studies of the sarcoplasmic reticulum Ca(2+)-ATPase are reviewed. More than 250 different point mutants have been expressed in cell culture and analysed by a panel of functional assays. Thereby, 40-50 important amino acid residues have been pinpointed, and the mutants have been assigned to functional classes: the Ca(2+)-affinity mutants, the phosphorylation-negative mutants, the ATP-affinity mutants, the E1P mutants, the E2P mutants, and the uncoupled mutants. Moreover, regions important to the specific inhibition by thapsigargin have been identified by analysis of Ca(2+)-ATPase/Na+,K(+)-ATPase chimeric constructs.