Immunological identification of a putative precursor of the insoluble glycoprotein framework of the Chlamydomonas cell wall.

To identify precursors of the insoluble glycoprotein framework of the Chlamydomonas cell wall, a polyclonal antibody was raised against the mixture of polypeptides released from the insoluble wall fraction by chemical deglycosylation. This antibody preferentially cross-reacted with a '150 kDa' salt-soluble cell wall glycoprotein. The conclusion that this '150 kDa' glycoprotein is a putative precursor of the insoluble cell wall fraction was corroborated by the results of pulse-chase experiments and by experiments with antibodies raised against the '150 kDa' salt-soluble glycoprotein and against its 100 kDa deglycosylation product, respectively. Whereas the antibody against the '150 kDa' glycoprotein preferentially recognized carbohydrate side chains, the antibody against its 100 kDa deglycosylation product was found to have essentially the same specificity towards glycosylated and deglycosylated cell wall components as the antibody against the deglycosylation products of the insoluble wall fraction. Furthermore, the antibody against the deglycosylated, insoluble wall fraction recognized almost the same set of peptide fragments derived by V8 protease treatment from the '150 kDa' salt-soluble cell wall glycoprotein and its 100 kDa deglycosylation product, respectively, as the antibody against the 100 kDa deglycosylated cell wall polypeptide.