Copyright The McGraw-Hill Companies inc.Permission required for reproduction or display 1 50 100 GGATCCTGgnTATTAAAAAGAAGATCTOTTTATTTAGAGATCTGTTnTATTGTGATCTCTTATTAGGATCGnnntnnnnTGTGGATAAgnngGATOCnnn GG CACTGOOC CAAG GGC G GC CGOCAGGC OOG TGT AG ACTCTCTA GTCG ACG AG T GCTTGICT GTCA GCG CGT A T GA T A TCGTGTTG GTGATTATTCAT 101 150 200 nTTt AAGATGAAnnnnnTggnAAGGATOncTAnCTGTGAATGATCGGTGATOCTGGnCCGTATAAGCTGGGATCAnAATGngGGnTTATACACAgCtCAA TT CAACC GGA AT A 9 G AG G AT M C●CIMEC4 AC 9 ACGCT AAG T GC CATAG AT AA G G GT G TG COGTT AAG GC TT TA AA G GA AA GAGAA GCOGTT CT C AC GGA 01 250 AAAncgnACaaCGGTTaTTCLTGGATAACTACCGGTTGATCCAAGCTInAnCAgAGTTATCCAAninG AnnGcnn-GAT:Consensus sequence CTGA AA A ⊙ CCTGA G GTA TC CAC Eschenichia GTGA AA 9 CC C G T ATG TC CAC Salm onella GCAT TC TG G GAA AGCTGOG Enterobacter TTCAGG AA TA G GAA AA TAT- Klebsie怕 AOGC TCG G G C TTA ACCAGAA TA G TTCA CT COG-A Erwinia col Pyoceedings of ie of USA 064-Ma1903) The minimal origin in E.coli is 245bp long
The minimal origin in E.coli is 245bp long．
How is replication initiated? Tandem array of Binding sites for DnaA protein, three 13 bp sequences four 9 bp sequences → → Consensus sequence Consensus sequence GATCTNTTNTTTT TTATCCACA DnaA protein binds to 9-mers(dnaA boxes) DnaA appears to facilitate the binding of DnaB to the origin. DnaA helps DnaB(helicase)bind at the origin by stimulating the melting of three 13-mer repeats at the left end of oriC to form an open complex(开放复合物) DnaC binds to DnaB and helps deliver it to the origin
How is replication initiated? • DnaA protein binds to 9-mers(dnaA boxes) • DnaA appears to facilitate the binding of DnaB to the origin． • DnaA helps DnaB (helicase)bind at the origin by stimulating the melting of three 13-mer repeats at the left end of oriC to form an open complex(开放复合物) • DnaC binds to DnaB and helps de1iver it to the origin．
20 DnaA bind 9 bp repeats oriC Four 9 bp Three 13 bp repeats repeats ATP DnaA (a)
20 DnaA bind 9 bp repeats
The A:T rich 13 bp repeats are denatured sequentially HU+ ATP (b)
The A:T rich 13 bp repeats are denatured sequentially
DnaB helicase binds the single stranded DNA 0+ ATP DnaB DnaC DnaB helicase (c) Priming and replication
DnaB helicase binds the single stranded DNA