title: The biogenesis of the cyanellae of Cyanophora paradoxa. II. Pulse-labelling of cyanellar polypeptides in the presence of transcriptional and translational inhibitors.
abstract: Cycloheximide and chloroamphenicol, specific inhibitors of protein translation in the cytoplasmic and cyanellar compartments, respectively, of Cyanophora paradoxa, have been employed in 30 min pulse-labelling experiments by using [NaH-14C]O3 to label total cell proteins in vivo. Cyanellae purified from host cell lysates were separated into soluble and thylakoid fractions and analysed by one- and two-dimensional polyacrylamide gel electrophoresis (PAGE) to determine the distribution of radioactivity in the cyanellar polypeptides. Analysis of the autoradiograms of electrophoretically resolved proteins of the cyanellae indicates that about 70% of the total number of cyanellar proteins visualized in the controls are synthesized on cytoplasmic ribosomes. The majority (81%) of the soluble cyanellar proteins appear to be cytoplasmically synthesized. In contrast, the majority (70%) of the thylakoid proteins are synthesized within the cyanellae. The observations also suggest that the polypeptides synthesized within the cyanellae include species that are the most abundant and rapidly turned over. A number of the polypeptides previously identified have now been characterized with regard to their sites of synthesis. In addition, we report on labelling experiments involving rifampicin, a specific inhibitor of cyanellar transcription, which indicate that different mRNAs within the cyanellae have markedly different stabilities.
authors.affiliation: Department of Biological Sciences, University of California, Santa Barbara 93106.
authors.forename: R L
authors.initials: RL
authors.lastname: Burnap
authors.forename: R K
authors.initials: RK
authors.lastname: Trench
mesh_terms: D001345:Autoradiography; D001639:Bicarbonates / Q000378:metabolism; D002250:Carbon Radioisotopes; D002701:Chloramphenicol / Q000494:pharmacology*; D003513:Cycloheximide / Q000494:pharmacology*; D015180:Electrophoresis, Gel, Two-Dimensional; D056890:Eukaryota / Q000187:drug effects / Q000378:metabolism* / Q000648:ultrastructure; D015388:Organelles / Q000378:metabolism*; D010452:Peptide Biosynthesis; D010455:Peptides / Q000235:genetics / Q000302:isolation & purification; D014176:Protein Biosynthesis / Q000187:drug effects; D012964:Sodium / Q000378:metabolism; D017693:Sodium Bicarbonate; D014158:Transcription, Genetic / Q000187:drug effects
chemical_list: D001639:Bicarbonates; D002250:Carbon Radioisotopes; D010455:Peptides; D002701:Chloramphenicol; D017693:Sodium Bicarbonate; D003513:Cycloheximide; D012964:Sodium