Bacteriophage λ replication proteins: Formation of a mixed oligomer and binding to the origin of λ DNA

✍ Scribed by Zylicz, Maciej ;Gorska, Izabella ;Taylor, Karol ;Georgopoulos, Costa

• Publisher: Springer
• Year: 1984
• Tongue: English
• Weight: 644 KB
• Volume: 196
• Category: Article
• ISSN: 0026-8925
• DOI: 10.1007/bf00436186

✦ Synopsis

The purified bacteriophage 2 replication proteins O and P sediment separately in metrizamide gradients of low ionic strength as dimers. Together they interact with each other forming an oligomer, composed of two molecules of 20 and one molecule of ,~P. The 20-P oligomer is active in the in vitro replication of ori2-containing DNA.

Equilibrium sedimentation in preformed metrizamide density gradients under conditions that separate DNA-protein complexes from free proteins was employed in order to study possible interactions among the 2 replication proteins and ori2 DNA. It was found that the 2P protein binds specifically to ori2-containing plasmid DNA only in the presence of ,~O protein. About 100 molecules of 20 and 10 molecules of 2P form a complex with the ori2 DNA. The 2 DNA-20-2P complex was shown to be active in an in vitro replication system.

Since the physical interactions between ori2 and 20 and between 2P and the Escherichia coli dnaB replication protein are well documented, the evidence for a 20-P interaction presented in this paper provides the missing link in the molecular mechanism that enables 2 to direct the host replication machinery to the replication of its own DNA.