[Show abstract][Hide abstract] ABSTRACT: ChemInform is a weekly Abstracting Service, delivering concise information at a glance that was extracted from about 100 leading journals. To access a ChemInform Abstract of an article which was published elsewhere, please select a “Full Text” option. The original article is trackable via the “References” option.
[Show abstract][Hide abstract] ABSTRACT: The cell wall of the unicellular green alga Chlamydomonas reinhardtii exclusively consists of hydroxyproline-containing glycoproteins. Protein chemical analysis of its polypeptide constituents was hindered by their cross-linking via peroxidase-catalysed intermolecular isodityrosine formation and transaminase-dependent processes. To overcome this problem, we have identified putative soluble precursors using polyclonal antibodies raised against deglycosylation products of the highly purified insoluble wall fraction and analysed their amino acid sequence. The occurrence of the corresponding polypeptide in the insoluble glycoprotein framework was finally probed by epitope mapping of the polyclonal antibodies using overlapping scan peptides which, together, cover the whole amino acid sequence of the putative precursor. As a control, peptide fragments released from the insoluble wall fraction by trypsin treatment were analysed by mass spectroscopy. By this approach, the heterodimeric, chaotrope-soluble glycoprotein GP3 proved to be a constituent of the insoluble extracellular matrix of Chlamydomonas reinhardtii. Furthermore, we have shown that the polypeptide backbones of both GP3 subunits are encoded by the same gene and differ by a C-terminal truncation in the case of GP3A.
[Show abstract][Hide abstract] ABSTRACT: A polyclonal antibody was raised against a recombinant Chlamydomonas 14-3-3-beta-galactosidase (beta-Gal) fusion protein and characterized for its epitope specificity towards the corresponding Chlamydomonas 14-3-3 protein by scan-peptide analysis. This antibody recognized four Chlamydomonas polypeptides with apparent molecular masses 32, 30, 27, and 24 kDa, which also reacted with the antiserum depleted of anti-(Escherichia coli beta-Gal) IgG, but not with the corresponding preimmune serum or the antiserum preincubated with purified 14-3-3 proteins. Western-blot analyses performed with the antibody depleted of anti-(beta-Gal) IgG revealed that more or less pronounced levels of 14-3-3 proteins were present in all subcellular fractions of Chlamydomonas reinhardtii except the nuclei. The highest levels of 14-3-3 protein were observed in the cytosol and microsomal fraction. The 30-kDa isoform was predominant in the cytosol, whereas the 27-kDa isoform was prevalent in the microsomes. When microsomal membranes were separated by sucrose-density-gradient centrifugation, Western-blot analysis revealed distinct patterns of 14-3-3 isoforms in the endoplasmic reticulum, dictyosome, and plasma membrane fractions identified by marker enzyme activities. These findings indicate that the four 14-3-3 proteins of C. reinhardtii differentially interact with endoplasmic reticulum, dictyosomes, and plasma membrane.
European Journal of Biochemistry 01/2002; 268(24):6449-57. · 3.58 Impact Factor
[Show abstract][Hide abstract] ABSTRACT: 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.
Plant and Cell Physiology 02/1996; 37(1):91-101. · 4.13 Impact Factor