Resting cyst wall glycoproteins isolated from two colpodid ciliates are glycine-rich proteins.

Two glycoproteins bands isolated from the cyst wall protein pattern of two colpodid ciliates, Colpoda inflata (gp46CI) and Colpoda cucullus (gp46CC) were analysed for their amino acid composition. Both glycoproteins are very rich in glycine and have a relatively high hydrophobicity, containing additionally many leucine and alanine residues. Their high degree of similarity is both quantitative and qualitative. Compared with just two previously published reports, their amino acid compositions are similar to those found in the hydrolysed cyst wall total proteins from the ciliates C. steinii and Paraurostyla spp. The amino acid composition corroborates that they are indeed glycoproteins, because asparagine, an amino acid residue suitable for the attachment to N-acetylglucosamine by its amide group (N-glycan), is abundant in both proteins. We discuss our data in relation to other glycine-rich proteins and a comparison with amino acid composition protein databases is carried out. Copyright 2000 Academic Press.