Biochemistry 2280A Study Guide - Final Guide: Helix-Turn-Helix, Catabolite Activator Protein, Tata-Binding Protein
30 Nov 2015
School
Department
Course
Professor
2280 Topic 24 I
Lac operon (look at notes)
• Negative control: Lac repressor (like trp with different
environmental signal)
• Positive control: catabolite activator protein (helix turn helix
like trp, activates through RNA polymerase)
6 Differences in Transcription Between Prokaryotes and
Eukaryotes
• People think b/c eukaryotes are bigger
1. Three RNA polymerases in eukaryotes
• Pol I most rRNA genes
• Pol II mRNAs
• Pol III tRNAs, 5s rRNA
• 1 RNA polymerase in prokaryotes
2. No operons in eukaryotes
• Each gene is transcribed as single unit – monocistronic
• Each promoter gives one gene product
• prokaryote – polycistronic
3. Promoter structure:
• Eukaryotic promoters do not have -10, -35 sequences – no
sigma
• Promoter recognition: determined by a set of proteins one of
which recognizes a TATA element
• Different factors to recruit RNA polymerase (Eu – TATA 2F2D,
Pro – sigma)
4. In eukaryotes regulatory proteins often bind DNA several thousand
base pairs from start site
• Eu – regulatory proteins can bind a long way – up to 10,000
base pairs from the start site of transcription
• How do proteins influence transcriptional machinery?
o When they are a long way from start site
o DNA can loop out – not stiff – bends so factors at distal
sites can influence transcription
o DNA looping
5. Combinational Control: groups of proteins work together to
determine the expression of a gene
• Most eu promoters influenced by many factors
o some + some –
o Some close some far
o Together determine expression
• A range of expression as much as 1000-fold can be achieved
o Prokaryotes – genes either on or off (trp)
find more resources at oneclass.com
find more resources at oneclass.com
