Deletion mutants of the B type natriuretic peptide receptor: cDNA expression and protein purification and characterization

The C type natriuretic peptide (CNP) is a peptide hormone stimulating vasor elaxation and inhibiting cell proliferation. CNP activates the type B natri uretic peptide receptor (NPR-B), known as the guanylate cyclase B membrane enzyme, which results in the cGMP release. To study functional properties o f NPR-B, its gene fragments were expressed in methylotrophic yeasts Pichia pastoris. Conditions were found providing for secretion of functionally act ive recombinant proteins NPR-Bs and NPR-B1 into the cultural medium in a yi eld of 25 mg/ml culture. Their specific activity was 0.97 and 0.93 mu mol c GMP min(-1) mg(-1) protein, respectively. It was shown that NPR-B belongs t o the family of Ser/Thr protein kinases and can be autophosphorylated at th e serine residues.