title: Purification and characterization of a putative sigma factor from Chalamydomonas reinhardi.
abstract: Two proteins with sigma-like activity have been isolated from the alga, Chlamydomonas reinhardi. One protein, sigma 2, has been partially purified and appears to have a molecular weight of 51,000. The interaction of this protein with a heterologous (Escherichia coli) and homologous (Chlamydomonas, chloroplast rifampicin-sensitive) core RNA-polymerase (RNA nucleotidyltransferase, nucleosidetriphosphate: RNA nucleotidyltransferase, EC 2.7.7.6) was studied. Sigma 2 protein appears to stimulate the formation of open (rapid starting) binary complexes by both of the core enzymes. Stimulation of transcription by sigma 2 on chloroplast DNA was greater when Chlamydomonas core enzyme was used. Moreover, in vitro transcription on a variety of templates using RNA polymerases I and II from Chlamydomonas was not stimulated by this protein.
mesh_terms: D002696:Chlamydomonas / Q000032:analysis* / Q000201:enzymology; D002736:Chloroplasts / Q000378:metabolism; D012321:DNA-Directed RNA Polymerases / Q000037:antagonists & inhibitors / Q000378:metabolism; D004926:Escherichia coli / Q000201:enzymology; D008970:Molecular Weight; D012293:Rifampin / Q000494:pharmacology; D012808:Sigma Factor / Q000302:isolation & purification* / Q000378:metabolism; D013698:Templates, Genetic; D014157:Transcription Factors / Q000302:isolation & purification*; D014158:Transcription, Genetic
chemical_list: D012808:Sigma Factor; D014157:Transcription Factors; D012321:DNA-Directed RNA Polymerases; D012293:Rifampin