Isolation and Characterization of a Ca exp 2+ Carrier Candidate from Calf Heart Inner Mitochondrial Membrane

摘要

A protein was isolated from calf heart inner mitochondrial membrane with the aid of an electron paramagnetic resonance assay based on the relative binding properties of Ca exp 2+ , Mn exp 2+ , and Mg exp 2+ to the protein. The molecular weight of this protein was estimated to be about 3000 by urea/sodium dodecyl sulfate gel electrophoresis and amino acid analysis. The protein had two classes of binding sites for Ca exp 2+ by flow dialysis studies. The dissociation constants of the high- and low- affinity binding sites for Ca exp 2+ were 9.5 and 33 mu M, respectively. This protein could extract Ca exp 2+ into an organic phase. The selectivity sequence of this protein determined from the organic solvent extraction experiments showed that it favored divalent cations over monovalent cations. Also, the relative selectivity sequence for divalent cations was Ca exp 2+ , Sr exp 2+ > Mn exp 2+ > Mg exp 2+ . Ruthenium red and La exp 3+ were shown to inhibit the protein-mediated extraction of Ca exp 2+ into the organic solvent. (ERA citation 04:047480)