Protein Kinase C ζ 4 Subspecies from Rat Brain: Its Structure, Expression, and Properties

• Published in: Proceedings of the National Academy of Sciences - PNAS 1989-05, Vol.86 (9), p.3099-3103
• Main Authors: Ono, Yoshitaka, Fujii, Tomoko, Ogita, Kouji, Kikkawa, Ushio, Igarashi, Koichi, Nishizuka, Yasutomi
• Format: Article
• Language: English
• Subjects: Biochemistry; Complementary DNA; COS cells; DNA; Enzymes; Open reading frames; Phorbol esters; Phosphatidylserines; Phospholipids; Plasmids
• ISSN: 0027-8424

The primary structure of the ζ subspecies of rat brain protein kinase C was deduced from its overlapping cDNAs. The ζ subspecies of protein kinase C consists of 592 amino acid residues with the calculated molecular mass of 67,740 Da and has regulatory and protein kinase domains in its amino- and carboxyl-terminal halves, respectively. Although all members of the protein kinase C family so far identified have a tandem repeat of the characteristic cysteine-rich zinc-finger-like sequence in the regulatory domain, the ζ subspecies contains only one set of this sequence. Northern (RNA)-blot hybridization analysis indicated that two major RNA transcripts of the ζ subspecies with different lengths may be generated by the use of different polyadenylylational signals. The enzyme was expressed in COS-7 cells by transfection with the cDNA construct encoding its whole sequence. It showed an approximate molecular mass of 64,000 Da upon SDS/PAGE. The enzyme activity was significantly dependent on phospholipid but was independent of the presence of Ca2+or diacyl-glycerol, when assayed with calf thymus H1 histone as a phosphate acceptor protein. The ζ subspecies expressed in COS-7 cells did not appear to show binding activity of phorbol ester. The structural and biochemical properties indicate that the ζ subspecies is related to, but distinct from, other subspecies of protein kinase C. Perhaps, this subspecies belongs to another entity of the enzyme family.