The beta-subunit of the bovine mitochondrial F1 ATPase specifically binds the amino terminal domain of parathyroid hormone.

A protein which specifically binds the amino terminal domain of parathyroid hormone (PTH) on nitrocellulose blots of polyacrylamide gels was fragmented with cyanogen bromide (CNBr), and two fragments were sequenced through 20 residues. The sequence obtained was 100% homologous with the beta-subunit of bovine F1 mitochondrial ATPase. Purified F1 ATPase from bovine heart and Escherichia coli were obtained and the binding of PTH examined on the blots. The beta-subunit of the bovine enzyme bound PTH specifically through its amino terminal domain. However, both the alpha- and beta-subunit of the E. coli enzyme were found to bind the hormone. This binding was also specific for the amino terminal domain of the hormone. The subcellular distribution of the PTH-binding protein from bovine kidney was also examined further. While the mitochondria and plasma membrane appear to possess similar PTH-binding capability, submitochondrial particles enriched in F1 ATPase were also enriched in PTH-binding activity.