摘要：

Based on previous in vivo genetic analysis of growth, we have developed two in vitro lambda systems composed entirely of purified proteins. One is termed '-independent' and consists of supercoiled lambda dv plasmid DNA, the lambda O and lambda P proteins, as well as the , , , , , DNA gyrase and holoenzyme proteins. The second system includes the protein and is termed '-dependent'. Both systems are specific for plasmid molecules carrying the ori lambda DNA initiation site. The major difference in the two systems is that the '-independent' system requires at least a 10-fold higher level of protein compared with the -dependent one. The lambda process may be divided into several discernible steps, some of which are defined by the isolation of stable intermediates. The first is the formation of a stable ori lambda-lambda O structure. The second is the assembly of a stable ori lambda-lambda O-lambda P-complex. The addition of to this complex also results in an isolatable intermediate. The , and proteins destabilize the lambda P-interaction, thus liberating 's activity, resulting in unwinding of the DNA template. At this stage, a stable intermediate can be isolated, provided that the protein has acted and/or is present. Following this, the primase enzyme recognizes the -complex and synthesizes primers. Subsequently, the primers are extended into DNA by holoenzyme. The proposed model of the molecular series of events taking place at ori lambda is substantiated by the many demonstrable protein-protein interactions among the various participants.

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