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Biochemical characterization of the boar sperm 42 kilodalton protein tyrosine kinase: Its potential for tyrosine as well as serine phosphorylation towards microtubule‐associated protein 2 and histone H 2B
Author(s) -
Berruti Giovanna
Publication year - 1994
Publication title -
molecular reproduction and development
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.745
H-Index - 105
eISSN - 1098-2795
pISSN - 1040-452X
DOI - 10.1002/mrd.1080380406
Subject(s) - biology , phosphorylation , tyrosine phosphorylation , microbiology and biotechnology , c raf , map2k7 , kinase , protein kinase a , protein phosphorylation , biochemistry , protein tyrosine phosphatase , mitogen activated protein kinase kinase , signal transduction , tyrosine , tyrosine kinase , cyclin dependent kinase 2
The majority of cellular responses to changing environmental conditions is regulated by protein kinases. Spermatozoa have many special properties, including motility with demonstrated chemotaxis, the ability to undergo capacitation, and the acrosome reaction, which are in part controlled by extracellular signals and in which sperm kinases are considered to be involved. We have previously reported that there is a protein kinase activity, which phosphorylates the synthetic substrate poly‐(Glu, Tyr) with a Km value of 2.3 μM, and is inhibited by the tyrosine kinase inhibitor tyrphostin, in the protein extract from boar spermatozoa (Berruti and Porzio, 1992: Biochim Biophys Acta 1118:149–154). Now we have demonstrated that the enzyme is cytosolic, is active as a monomer of M r 42,000, is stimulated by Mg 2+ > Mn 2+ but not by Ca 2+ , is renaturable, and can phosphorylate native protein substrates such as microtubule‐associated protein 2 (MAP2) and histone H2B both on the tyrosine and serine residues. N‐terminal sequence analysis suggests that it is a novel protein. These new findings imply that the boar sperm 42 kD kinase may be a novel member of the emerging class of dual‐specificity protein kinases, and they raise the intriguing question of its function in the protein kinase network mediating signal transduction in mammalian spermatozoa. © 1994 Wiley‐Liss, Inc.