title: Protein kinase A-dependent phosphorylation of B/K protein.
abstract: We have previously isolated a novel protein "B/K" that contains two C2-like domains. Here, we report the isolation and mRNA distribution of a human B/K isoform, and protein kinase A (PKA)-dependent phosphorylation of the B/K protein. The 1.5 kb human B/K cDNA clone exhibits 89% and 97% identities with rat B/K in the sequences of nucleotide and amino acid, respectively. Human B/K isoform encodes a 474 amino acid protein and shows structural features similar to the rat counterpart including two C2 domains, three consensus sequences for PKA, absence of a transmembrane region, and conservation of the N-terminal cysteine cluster. On Northern and dot blot analyses, a 3.0 kb B/K transcript was abundantly present in human brain, kidney, and prostate. Among the brain regions, strong signals were observed in the frontal and temporal lobes, the hippocampus, the hypothalamus, the amygdala, the substantia nigra, and the pituitary. Recombinant B/K proteins containing three consensus sites for PKA was very efficiently phosphorylated in vitro by PKA catalytic subunit. B/K protein which was overexpressed in LLC-PK1 cells was also strongly phosphorylated in vivo by vasopressin analog DDAVP, and PKA-specific inhibitor H 89 as well as type 2 vasopressin receptor antagonist specifically suppressed DDAVP-induced B/K phosphorylation. These results suggest that B/K proteins play a role as potential substrates for PKA in the area where they are expressed.
authors: National Eye Institute, National Institutes of Health, Bethesda, MD 20892, USA.
authors: Hemin
authors: H
authors: Chin
authors: Sung Ho
authors: SH
authors: Choi
authors: Yoon Seong
authors: YS
authors: Jang
authors: Sung Min
authors: SM
authors: Cho
authors: Ho Shik
authors: HS
authors: Kim
authors: Jeong Hwa
authors: JH
authors: Lee
authors: Seong Whan
authors: SW
authors: Jeong
authors: In Kyung
authors: IK
authors: Kim
authors: Grace J
authors: GJ
authors: Kim
authors: Oh Joo
authors: OJ
authors: Kwon