PMID: 2502031Jul 1, 1989Paper

Trypsin activation of atrial muscarinic K+ channels

The American Journal of Physiology
G E Kirsch, A M Brown

Abstract

The atrial muscarinic K+ channel normally is opened by the activated G protein, Gk. Based on the assumption that an inactivating particle keeps the channel closed, several protein-modifying agents including trypsin, papain, glyoxal, and phenylglycoxal that remove Na+-channel inactivation were tested. K+ channels were studied in inside-out excised membrane patches from primary cultures of neonatal rat atrial myocytes. Of the agents tested, only trypsin activated muscarinic K+ channels, and it did so irreversibly. Trypsin was effective in the absence of muscarinic agonist or intracellular Mg2+ and guanosine 5'-triphosphate. Heat-denatured trypsin was ineffective, and trypsin inhibitor blocked the effect. Because trypsin is known to inactivate G proteins, the effect was probably on the K+ channel or a structure closely associated with it. Trypsin activation produced single-channel currents in which inward rectification, single-channel conductance, mean open time, and burst duration were indistinguishable from muscarinic activation. Trypsin cleaves proteins at lysine or arginine residues, and the arginine-specific reagents, glyoxal and phenylgloxal, did not activate K+ channels. We conclude that trypsin disrupts an inhibitory gatin...Continue Reading

Citations

Sep 8, 1994·Nature·L Y Jan, Y N Jan
May 18, 2001·American Journal of Physiology. Heart and Circulatory Physiology·Z ShuiM R Boyett
Jun 4, 2004·The Journal of Biological Chemistry·Sergej MilovicLukas G Weigl

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