Title : The disulfide linkages and glycosylation
sites of the human
natriuretic peptide receptor-C homodimer
Abstract :
- The natriuretic peptide receptor-C ( NPR-C ) constitutes greater than 95% of the natriuretic peptide binding sites in vivo
- This cell surface glycoprotein is a disulfide-linked homodimer with a subunit molecular weight of 68,000
- Two sources and types of ANP affinity-purified human NPR-C were used to map disulfide linkages and glycosylation sites of this receptor by mass spectrometry: the extracellular domain obtained by papain cleavage of a receptor- IgG fusion protein expressed in Chinese hamster ovary cells, and a baculovirus/Sf9-expressed cytoplasmic truncation mutant in which 34 of 37 cytoplasmic domain amino acids were deleted
- Two intramolecular disulfide bonded loops were found in the 435 amino acid extracellular domain ( C63-C91, C168-C216 )
- The juxtamembrane residues C428 and C431 are involved in homodimer formation, confirmed by site-directed mutagenesis of full-length NPR
- Three of the four potential Asn-linked glycosylation sites are occupied: N41 (complex), N248 (high mannose) , and N349 (complex; partial occupancy)
- These data describe the intra- and intermolecular linkages in NPR-C , providing a model for the homologous guanylyl cyclase receptors , NPR-A and NPR-B ; both of the cyclase receptors likely contain the first amino-terminal 29 amino acid loop, but only NPR-A possesses the second 49 amino acid loop in common with NPR-C