ANTIBODIES RAISED AGAINST A PEPTIDE CORRESPONDING TO A G(SA) DOMAIN REVEAL A VIMENTIN-ASSOCIATED PROTEIN

In an attempt to localize the guanine nucleotide binding protein G(sal pha) by immunocytochemistry, we synthetized peptides corresponding to several stretches of residues deduced from the published cDNA sequence of G(salpha) and raised antibodies against them. Among the peptides, one corresponding to residues 367-381 elicited antibodies that immunoc ytochemically detected, at the optical level, what appeared to be vime ntin in several cells and tissues. Studies at the ultrastructural leve l confirmed this observation and also showed weak staining of some are as of plasma membranes of glial and nerve cells. Analysis by Western b lots of rat brain subcellular fractions indicated that: (a) the protei n stained by the anti-peptide antibodies was associated with the cysto skeleton; and (b) it was not vimentin but a protein of higher molecula r weight, 65 KD. We accordingly suggest that the G(salpha)-derived pep tide elicited two types of antibodies, one recognizing G(salpha), in f ixed tissues, the other recognizing an epitope located in a vimentin-a ssociated protein. This study emphasizes the caution that is needed wh en conclusions are drawn on the basis of immunocytochemical studies us ing anti-peptide antibodies.