Search

We designed a screen to identify starfish oocyte proteins able to bind monomeric cyclin B by affinity chromatography on a cyclin B splice variant displaying low affinity for cdc2. We identified a 15 kDa protein previously described as a cdk-binding protein [Biochim. Biophys. Acta Mol. Cell Res. 1589 (2002) 219–231]. Cybip is encoded by a single polymorphic gene and the native protein is matured by cleaving a signal peptide. We firmly establish the fact that it is a true cyclin B-binding protein, since the recombinant protein binds recombinant cyclin B in absence of any cdk. Finally, we show that the microinjection of GST-cybip, and of anti-cybip antibody, in maturing starfish oocytes, inhibits H1 kinase and MPF inactivation, and first polar body emission.

βIGH3 protein has been recently involved in the pathogenesis of blinding corneal diseases, some of which have characteristic amyloid corneal deposits. The 124 codon of the βig-h3 gene seems to be crucial for the amyloidogenicity of the protein product. We presently report an in vitro system that reproducibly forms amyloid fibrils from βIGH3 (110–131) derived peptides. We also assessed the differences in fibril formation of two 22-amino acid peptides centered on the 124 residue: the native form and the Arg124Cys peptide (mutation linked to lattice corneal amyloid dystrophy type 1). After dialysis of Arg124Cys peptide against PBS 1/15 M pH 7.4 for 72 hours, Congo red staining and electron microscopy demonstrated the presence of abundant material fulfilling the criteria of amyloid. Quantitative analysis with thioflavine T fluorescence studies confirmed the high capacity of Arg124Cys peptide to form amyloid fibrils when compared to the native form.

A 67 kDa actin-binding protein was isolated from bovine aorta. Partial amino acid sequence determination of two large thermolysin peptides were used to compare 67 kDa bovine aorta protein and p36 the substrate of pp60src tyrosine kinase. Sequence analysis shows that 67 kDa bovine aorta protein shares common domains with p36 and possesses the consensus aminoacid sequences of mammalian Ca2+-dependent membrane-binding protein and p36/gelsolin.