Fig. 7.

The nonreceptor tyrosine kinase FYN and several low and high molecular weight GTP-binding proteins co-fractionate with caveolin-containing fractions. A, Equal volumes of fractions collected across a detergent gradient were resolved by SDS-PAGE and processed for immunoblot analyses using anti-FYN mAb. An immunoreactive band of 59 kDa is enriched in fraction 5, which corresponds to the peak gradient fraction of caveolin.B, Equal volumes of fractions collected across a detergent gradient were fractionated by SDS-PAGE, transferred to nitrocellulose, and probed with [³²P]GTP. Labeled proteins are concentrated in the 22–31 kDa molecular weight range. Only one set of GTP-bound proteins appears to co-fractionate with the caveolae fractions (arrow). C, Equal volumes of fractions collected across a detergent gradient were labeledin situ using periodate-oxidized [α-³²P]GTP, and polypeptides were separated by SDS-PAGE. In contrast to that observed in the GTP-overlays, multiple proteins of high apparent molecular weight are labeled. Although most of the labeled proteins remain in the load fractions, several high molecular weight proteins co-isolate with the caveolae fractions (arrows). Molecular mass × 10⁻³ is indicated vertically; fraction number is indicated horizontally.