Characterization and subcellular distribution of G-proteins in highly purified 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-catalyzed ADP-ribosylation and by immunoblots. Two B. pertussis toxin substrates were present in transverse tubules and sarcoplasmic reticulum from frog and rabbit skeletal muscle. Immunoblot analysis suggested that the two B. pertussis toxin substrates present in rabbit sarcoplasmic reticulum are possibly alpha i2 and alpha i3, but the corresponding substrates in sarcoplasmic reticulum from frog are still unidentified. Transverse tubules isolated from both rabbit and frog also contained alpha i2 and alpha i3; additionally, beta 35, beta 36, alpha o (weak immunoreactivity), alpha i1 (and/or alpha i3 in frog), alpha s (short form only in frog), and alpha q were found. Sarcoplasmic reticulum from rabbit also contained alpha s (predominantly alpha s short), beta 36, and alpha q. The presence of alpha q 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-contraction coupling in skeletal muscle.
Carrasco
M A
MA
Departamento de Fisiología y Biofísica, Facultad de Medicina, Universidad de Chile.
Sierralta
J
J
de Mazancourt
P
P
D000246:Adenosine Diphosphate Ribose / Q000378:metabolism; D000595:Amino Acid Sequence; D000818:Animals; D002451:Cell Compartmentation; D019204:GTP-Binding Proteins / Q000032:analysis* / Q000276:immunology; D008969:Molecular Sequence Data; D009132:Muscles / Q000737:chemistry*; D010446:Peptide Fragments / Q000276:immunology; D037342:Pertussis Toxin; D011487:Protein Conformation; D011817:Rabbits; D011898:Ranidae; D012519:Sarcoplasmic Reticulum / Q000737:chemistry; D013347:Subcellular Fractions / Q000737:chemistry; D010566:Virulence Factors, Bordetella / Q000378:metabolism
D010446:Peptide Fragments; D010566:Virulence Factors, Bordetella; D000246:Adenosine Diphosphate Ribose; D037342:Pertussis Toxin; D019204:GTP-Binding Proteins