trinsic terminators include palindromic regions that from hairpins varying in length from 7 to 20 bp. The stem-loop structure includes a G-C-rich region and is followed by a run of U residues CG C G G-C-nich region in stem C G C G
Intrinsic terminators include palindromic regions that from hairpins varying in length from 7 to 20 bp.The stem-loop structure includes a G-C-rich region and is followed by a run of U residues
Yeast RNA polymerase has grooves that could be binding sites for nucleic acids. The pink beads show a possible path for DNA that is 25A wide and 5 10A deep. The green beads show a narrower channel, 12-15A wide and -20A deep, that could hold RNA Photograph kindly provided by roger Kornberg
Yeast RNA polymerase has grooves that could be binding sites for nucleic acids.The pink beads show a possible path for DNA that is ~25Å wide and 5- 10Å deep.The green beads show a narrower channel,12-15Å wide and ~20Å deep,that could hold RNA.Photograph kindly provided by Roger Kornberg
Eubacterial rNa polymerase have four types of subunit a, B, and B have rather constant sizes in different bacterial species, but o varies more widely Gene product Functions enzyme assembly rpoA 2 a subunits promoter recognition (40 KD each) binds some activators rpoB阝 subunit (155kD) roc阝 subunit catalytic center (160kD) rpoD o subunit (3290kD) promoter specificity 入入 E. coli enzyme 465kD
Eubacterial RNA polymerase have four types of subunit; α,β,and β’ have rather constant sizes in different bacterial species,but σ varies more widely
E coli sigma factors recognize promoters with different consensus sequences. (Numbers in the name ofa factor indicate its mass) Ge ene Factor Use -35 Sequence Separation 10 Sequence D 70 general TTGACA 16-18bp TATAAT rpo heat shock CCCTTGAA 13-15bp CCCGATNT rpoE heat shock not known not known not known rpoN nitrogen CTGGNA 6 b TTGCA fliA flagellar CTAAA 15b GCCGATAA A map of the E coli o70 factor Core enzyme identifies conserved binding Melting regions. Regions 2. 1 and 2.2 个个 contact core polymerase. 2.3N-terminus 200 0 600 is required for melting and 2.4 and 4.2 contact the -10 1.11.2 2.124 4.14.2 and -35 promotor Interactions with promoter elements. The N-terminal region prevents 2.4 and 4.2 pRevents DNA-binding from binding to DNA in the -10 35 bsence of core enzyme TAATAT ACAGTT 5
A map of the E.coli σ 70 factor identifies conserved regions.Regions 2.1 and 2.2 contact core polymerase,2.3 is required for melting,and 2.4 and 4.2 contact the -10 and -35 promotor elements.The N-terminal region prevents 2.4 and 4.2 from binding to DNA in the absence of core enzyme. E.colisigma factors recognize promoters with different consensus sequences.(Numbers in the name of a factor indicate its mass)
One face of the promoter contains the contact points for RNA -35 sequence -10 sequenc ↓↓↓↓↓↓↓↓ ↓↓↓ ↓↓↓ I Modification prevents XXXTTGACA Nontemplate strand RNA polymerase binding 4:李李 Unwinding ↑ RNA polymerase XXXXXX AACTG T XXXXXXXXXXXXXXXXXATA Template strand X XXXXXX protects against mod ification TTAXXXXXXX CX Mutations abolish or reduce promoter activity oints of contact lie on one face of DNA (on the nontemplate strand) 八 MN
One face of the promoter contains the contact points for RNA