Distribution of the alpha-subunit of the guanine nucleotide-binding protein Gi2 and its comparison to G alpha o.

Abt. Neuropharmakologie, Max-Planck-Institut für Psychiatrie, Martinsried, FRG.

Site specific antisera against a synthetic peptide corresponding to the sequence 3-17 of G alpha 12 have been raised and the specificity examined using purified homogeneous Go, Gi2 and Gi containing a 41 kDa alpha-subunit. The distribution of G alpha i2 was investigated in plasma membranes from different tissues and cells and compared to the distribution of G alpha o and other pertussis toxin sensitive G alpha. Considerable amounts of G alpha i2 were found in endocrine tissue especially in membranes from the adrenal and thyroid, in leucocytes and platelets where it constitutes the major, if not only, pertussis toxin-sensitive G alpha, as well as in some cell lines (C6, NG 108-15, S49 cyc-); erythrocytes contained a 41 kDa G alpha i which was different from G alpha i2. G alpha o was present abundantly in nervous tissue, adrenal medulla and cortex but also found in low amounts in other membranes except for lung, liver and blood cells. Subcellular fractionation of cardiac ventricular muscle demonstrated the presence of G alpha o and low amounts of G alpha i2 in sarcolemma, but only 41kDa G alpha i was present in sarcoplasmic reticulum. The importance of the distinct distribution in terms of signal transduction is discussed.

PMID: 2512386 [PubMed - indexed for MEDLINE]