Structural characteristics of the 35- and 36-kDa forms of the beta subunit common to GTP-binding regulatory proteins

MJ Woolkalis and DR Manning

The beta subunit common to GTP-binding regulatory proteins can be resolved into immunologically distinct proteins typically referred to as 35- and 36-kDa forms of the subunit. The extent to which these two forms are structurally related was examined by isoelectric focusing, nonequilibrium pH gradient electrophoresis (NEPHGE), and two- dimensional peptide mapping. Each of the two forms of the beta subunit isolated from rabbit liver was found to comprise species of protein having isoelectric points of 5.7, 5.8, and 5.95; those having an isoelectric point of 5.8 were the most prominent. The beta subunits isolated from bovine brain and rod outer segments exhibited species having identical isoelectric points. Similar patterns of species were also noted for forms of the beta subunit detected immunologically within diverse types of cells. Analysis of the 35- and 36-kDa forms of the beta subunit by NEPHGE confirmed the absence, with only minor exceptions, of other constituent proteins. Subjection of chymotryptic peptides to high voltage electrophoresis and chromatography on cellulose revealed similarities, as well as differences, between the two forms of the beta subunit. These data provide evidence that the 35- and 36-kDa forms of the beta subunit are indeed structurally related and are conserved among diverse types of cells.

Volume 32, Issue 1, pp. 1-6, 07/01/1987
Copyright © 1987 by American Society for Pharmacology and Experimental Therapeutics