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Insect Biochem Mol Biol. 2002 Aug;32(8):847-57.

Cyclic nucleotide-independent phosphorylation of vitellin by casein kinase II purified from Rhodnius prolixus oocytes.

Author information

1
Departamento de Bioquímica Médica, Instituto de Ciências Biomédicas, Centro de Ciências da Saúde, Universidade Federal do Rio de Janeiro, UFRJ, Cidade Universitária, Rio de Janeiro, RJ, CEP 21941-590, Brazil. maneto@bioqmed.ufrj.br

Abstract

In this study we show that Vitellin (VT) phosphorylation in chorionated oocytes of Rhodnius prolixus is completely inhibited by heparin (10 microg/ml), a classical casein kinase II (CK II) inhibitor. VT phosphorylation is not affected by modulators of cyclic nucleotide-dependent protein kinases such as c-AMP (10 microM), H-8 (1 microM) and H-89 (0.1 microM). We have obtained a 3000-fold VT-free enriched preparation of CK II. Autophosphorylation of this enzyme preparation in the presence of (32)P-ATP demonstrated that it lacks any endogenous substrates. Rhodnius CK II is strongly inhibited by heparin (Ki = 9 nM) and uses ATP (Km = 36 microM) or GTP (Km = 86 microM) as phosphate donors. Incubation of VT with purified Rhodnius CK II and (32)P-ATP led to the incorporation of 2 mols of phosphate/mol VT. However, the total number of phosphorylation sites available can be altered by previous incubation of VT with alkaline phosphatase. These data show that an insect yolk protein contain phosphorylation sites for a cyclic nucleotide-independent protein kinase such as CK II.

PMID:
12110292
DOI:
10.1016/s0965-1748(01)00173-4
[Indexed for MEDLINE]

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