CHARACTERIZATION AND SUBCELLULAR-DISTRIBUTION OF G-PROTEINS IN HIGHLYPURIFIED SKELETAL-MUSCLE FRACTIONS FROM RABBIT AND FROG

The presence of G-proteins in highly purified fractions from frog and rabbit skeletal muscles was analyzed by Bordetella pertussis toxin-cat alyzed ADP-ribosylation and by immunoblots. Two B. pertussis toxin sub strates were present in transverse tubules and sarcoplasmic reticulum from frog and rabbit skeletal muscle. Immunoblot analysis suggested th at the two B. pertussis toxin substrates present in rabbit sarcoplasmi c reticulum are possibly alphai2 and alphai3, but the corresponding su bstrates in sarcoplasmic reticulum from frog are still unidentified. T ransverse tubules isolated from both rabbit and frog also contained al phai2 and alphai3; additionally, beta35, beta36, alphao (weak immunore activity), alphai1 (and/or alphai3 in frog), as (short form only in fr og), and alphaq were found. Sarcoplasmic reticulum from rabbit also co ntained alphas (predominantly alphas short), beta36, and alphaq. The p resence of alphaq in sarcoplasmic reticulum, in addition to transverse tubules, is potentially a very important finding since this G-protein has been described only in plasma membranes so far. Also, this study describes the candidate G-proteins for the control of excitation-contr action coupling in skeletal muscle. (C) 1994 Academic Press, Inc.