Phosphorylation of bovine brain 81-kDa acidic calmodulin binding protein (ACAMP-81) in vitro

Hiroshi Tokumitsu, Akihiro Mizutani, Masato Watanabe, Hiroyoshi Hidaka

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5 Citations (Scopus)


We found a novel 81-kDa acidic protein (ACAMP-81) in the bovine brain membrane fraction, which bound to calmodulin in a Ca2+-dependent manner. The present study reveals physicochemical properties and phosphorylation of this protein with various protein kinases in vitro. The Stokes radius and sedimentation coefficient were calculated to be 52 Å and 2.05 S, respectively, suggesting that the structure of ACAMP-81 is highly elongated. Purified Ca2+/phospholipid-dependent protein kinase (protein kinase C), cAMP-dependent protein kinase, and Ca2+/calmodulin-dependent protein kinase II (Ca2+/ CaM kinase II) catalyzed the incorporation of 1.46, 0.72, and 0.44 mol of phosphate/mol of ACAMP-81, respectively. The amino acid residues of ACAMP-81 phosphorylated by either protein kinase C or cAMP-dependent protein kinase were almost exclusively on serine. Sequential phosphorylation of ACAMP-81 by cAMP-dependent protein kinase and protein kinase C resulted in the additional incorporation of 1.15 mol of [32P]phosphate into ACAMP-81. Comparison of phosphopeptide maps of ACAMP-81 phosphorylated by each kinase revealed that there are two classes of phosphorylatable polypeptide, one is phosphorylatable by both protein kinases which contained two polypeptides and the others are specific sites for protein kinase C.

Original languageEnglish
Pages (from-to)94-98
Number of pages5
JournalArchives of Biochemistry and Biophysics
Issue number1
Publication statusPublished - Apr 1991
Externally publishedYes

ASJC Scopus subject areas

  • Biophysics
  • Biochemistry
  • Molecular Biology


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