FIG. 4.
Characterization of the BIC-C protein in Bic-C alleles. (A) A schematic representation of the BIC-C protein is shown. S/G, serine-glycine-rich region. Letters indicate the sites of mutations found in the following Bic-C alleles: a, AB79, deletion of amino acids 226 to 278; b, RU35, G296R; c, IIF34, protein truncated at 574 plus 27 new amino acids. Schematics of two other proteins used in RNA-binding experiments, BIC-CG296R and KH 1–3, are also shown. Numbers represent amino acid positions in the protein. (B) Western analysis of BIC-C protein in Bic-C alleles. Ovaries were taken from either Oregon-R (OreR) or transheterozygotes of the indicated Bic-C allele and Df(2L)RA5. Ten micrograms of ovary extract was analyzed by SDS–8.5% PAGE followed by immunoblotting. Bic-C alleles are presented in decreasing order of strength for the dominant embryonic patterning phenotype (31) from left to right. The arrowheads indicate BIC-C proteins; the 100-kDa band is the cross-reacting protein also recognized by the anti-BIC-C antibody. Under these conditions, only the major BIC-C isoform (120 kDa) is seen. Molecular size markers are indicated in kilodaltons.