PCB 3063 Lecture Notes - Lecture 29: Sigma Factor, Enzyme, Ribosomal Rna
Document Summary
Catalyzes synthesis of all classes of rna in bacteria. Once a few rntps are synthesized, it detaches to be used again. Euk-rna pol ii transcribes pre- mrnas, snornas, snrnas. Euk-rna pol iii transcribes trnas, small rrna, snrnas. 3 stages of transcription: initiation, elongation, termination. Prok initiation transcription apparatus assembles on promoter & begins synthesis of rna: promoter recognition, transcription bubble forms, first rntp bonds form, transcription apparatus "escapes" from the promoter. Go down each column & use the most common letters: gat. Mutations or base substitutions at -10 or -35 consensus means a reduced rate in transcription (down mutations) Rna pol has a conformational change and moves downstream after initiation. Rna pol unwinds dna ( transcriptional bubble) & rewinds after transcript is made. Only about 18 nts unwound at a time; The dna sequence produces a pause; sequence allows protein to bind; terminates transcription. Have inverted repeats; some have aaaa following inverted repetitive sequence.
