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Molecular cloning and enzymatic analysis of the rat homolog of "PhK-gamma T," an isoform of phosphorylase kinase catalytic subunit.

Authors: Calalb, MB  Fox, DT  Hanks, SK 
Citation: Calalb MB, etal., J Biol Chem 1992 Jan 25;267(3):1455-63.
Pubmed: (View Article at PubMed) PMID:1370475

Messenger RNA encoding a protein kinase closely related to the catalytic subunit of skeletal muscle phosphorylase kinase has previously been isolated from a human HeLa cell cDNA library, and cross-species Northern hybridization analysis has shown that the rat homolog of this transcript is abundant in the adult testis (Hanks, S.K. (1989) Mol. Endocrinol. 3, 110-116). We now propose that the protein encoded by this transcript be designated as "PhK-gamma T." In this article, the primary structure of the rat homolog of PhK-gamma T is described, as deduced from nucleotide sequences of cDNA and genomic clones. RNase protection analysis reveals that PhK-gamma T transcripts are actually present in a wide variety of adult rat tissues, but at levels 20-100-fold less than what is observed in the testis. In the testis, transcription of the PhK-gamma T gene is initiated at multiple sites as shown by RNase protection and primer extension. Enzymatic activity of PhK-gamma T was demonstrated using renatured bacterially expressed protein. In the presence of Ca2+/calmodulin, PhK-gamma T is able to efficiently phosphorylate glycogen phosphorylase and convert it from an inactive to an active form. We conclude that PhK-gamma T represents a true isoform of phosphorylase kinase catalytic subunit.


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CRRD Object Information
CRRD ID: 727546
Created: 2003-10-31
Species: All species
Last Modified: 2004-05-25
Status: ACTIVE


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