Tussle with a terminator

摘要

TOWARDS the end of a round of replication of a circular bacterial chromosome, two approaching replication forks are forced to meet within a restricted 'terminus' region, approximately opposite the origin. This is achieved through the presence of a replication-fork arrest system in this region (Fig, 1). Such systems were first discovered, and have been most extensively characterized, in Escherichia coli and Bacillus subtilis, and it is likely that they allow the more efficient coupling of chromosome replication and cell division. The two'bacterial systems each comprise several short DNA terminators (Ter) of 20-30 base pairs, plus a cognate terminator protein that recognizes Ter sites and binds to them tightly.