Open AccessEvidence for a "mute" catalytic subunit of cyclic AMP-dependent protein kinase from rat muscle and its mode of activation.
Author(s) -
M. Gagelmann,
Jennifer Reed,
Dieter Kübler,
Walter Pyerin,
V. Kinzel
Publication year - 1980
Publication title -
proceedings of the national academy of sciences of the united states of america
Language(s) - English
Resource type - Journals
eISSN - 1091-6490
pISSN - 0027-8424
DOI - 10.1073/pnas.77.5.2492
Subject(s) - isoelectric point , protein subunit , protein kinase a , isozyme , biochemistry , enzyme , gamma subunit , isoelectric focusing , enzyme activator , pi , chemistry , biophysics , biology , gene
An isoenzyme of the catalytic subunit of type II cyclic AMP-dependent protein kinase from rat muscle is reported which coelutes with the classical catalytic subunit but differs from it in isoelectric point (pI 8.7 vs pI 9.1) and is enzymmatically inactive. After reaction with a heat- and acid-stable component of the protein kinase modulator fraction from the same tissue, the "mute" isoenzyme displays a high activity when assayed on isoelectric focusing gels. This activation process does not occur through proteolytic degradation and is not characteristic of a turnover-type reaction. The data imply direct interaction between the isoenzyme and a modulating protein which may subsequently be separated from the enzyme without reversal of the activation. The modulator protein thus appears to act as a template, inducing a conformational change. The implications of such a mute isoenzyme and its control through small modulator proteins are discussed.