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This Article Full Text (PDF) Alert me when this article is cited Alert me if a correction is posted Services Email this article to a friend Similar articles in this journal Similar articles in PubMed Alert me to new issues of the journal Download to citation manager Rights and Permissions Citing Articles Citing Articles via HighWire Citing Articles via CrossRef Citing Articles via Google Scholar Google Scholar Articles by Stoehr, S. J. Articles by Smolen, J. E. Search for Related Content PubMed PubMed Citation Articles by Stoehr, S. J. Articles by Smolen, J. E. Social Bookmarking                   What's this?  Previous Article  |  Table of Contents  |  Next Article  Human neutrophils contain a protein kinase C-like enzyme that utilizes guanosine triphosphate as a phosphate donor. Cofactor requirements, kinetics, and endogenous acceptor proteins SJ Stoehr and JE Smolen Department of Pediatric Hematology/Oncology, University of Michigan, Ann Arbor 48109. Investigations of protein kinase C (PKC) activity have focussed on protein phosphorylation using adenosine triphosphate (ATP), not guanosine triphosphate (GTP), as the phosphate donor. In a continuing study of the enzymology of the PKC of human neutrophils, we wanted to determine if there might be protein kinases that do use GTP as a phosphate donor. Soluble extracts or detergent-extracted fractions of human neutrophils were used as enzyme sources. Phosphorylation of histone using [gamma-32P]-GTP was 31% as effective as [gamma-32P]-ATP. Phosphorylation with GTP depended on Ca2+, Mg2+, and phospholipid, just as the ATP, and the Ca2+ requirements were similar. In all cases, H-7, an inhibitor of ATP-supported PKC activity, blocked GTP-utilizing activity. Sodium dodecyl sulfate-polyacrylamide gel electrophoresis (SDS-PAGE) revealed that similar endogenous proteins were phosphorylated with ATP or GTP. The apparent Km and Vmax for the enzyme(s) for both phosphate donors were identical, although these were modified by treatment with Triton X-100. GTP competitively inhibited use of ATP by PKC; however, low concentrations of ATP enhanced GTP- utilizing kinase activity in some cases. Non-hydrolyzable forms of ATP and other nucleotide triphosphates were inhibitory. Detergent treatment also markedly altered the number of proteins phosphorylated by either nucleotide. The major protein phosphorylated in the soluble or detergent extract was a single polypeptide band in the 34 Kd range. These studies are the first to explicitly examine the possible phosphorylation by neutrophil PKC using GTP and point to a potential alternative mode of enzyme activity. Since high concentrations of GTP are available within neutrophils, the ability of PKC or a PKC-like enzyme to use this nucleotide may have important ramifications in signal transduction. Volume 75, Issue 2, pp. 479-487, 01/15/1990 Copyright © 1990 by The American Society of Hematology CiteULike    Connotea    Del.icio.us    Digg    Reddit    Technorati    What's this? This article has been cited by other articles: Y. Liu, S. A. Bohn, and J. L. Sherley Inosine-5'-Monophosphate Dehydrogenase Is a Rate-determining Factor for p53-dependent Growth Regulation Mol. Biol. Cell, January 1, 1998; 9(1): 15 - 28. [Abstract] [Full Text]

	Copyright © 1990 by American Society of Hematology         Online ISSN: 1528-0020