Development-dependent expression of low molecular weight GTP-binding proteins in embryonic chicken brain.

Expression of low molecular weight GTP-binding proteins in particulate and soluble fractions of embryonic chicken brain was analysed by SDS-PAGE and incubation of blotted proteins with [alpha-32P]GTP. At least seven GTP-binding proteins with apparent molecular weights between 21 and 29 kDa were demonstrated by this technique in membranes and microsomal fractions, whereas only four species were present in the cytosol. Levels of several small GTP-binding proteins were developmentally regulated in membrane and microsomal fractions, but not in the cytosol of embryonic chicken brain. Major GTP-binding proteins G28 and G26 were strongly increased in microsomal but not in membrane fractions between E6 and hatched chicken brain, whereas the minor protein G24 decreased in both membrane and microsomal fractions over this time. The differential expression of low molecular weight GTP-binding proteins in embryonic chicken brain suggests important roles for these proteins in brain development.