DIRECT IMAGING OF E.coil POLYMERASE AND TRANSCRIPTION COMPLEX WITH PROMOTER REGION OF MUTANT DNA (UV5).

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Improved low angle rotary shadowing was available for structural analysis of RNA polymerase and its binding to DNA (transcription complex). The shadowed image of the polymerase was basically composed of four subunits in two different sizes and one rod like structure. A dimeric structure of two big subunits was stacked on another small dimeric structure, forming large channel between them, 3nm in width. Rod like structure was found in this channel. Big and small subunits seem to correspond to b, b^ユ and 2 a subunits respectively, judging from differences in their molecular weight that have been revealed biochemically so far. On binding with the promoter region of DNA,DNA strand was found in this large channel. Comparative observation of core enzyme without s factor suggested that s factor should be rod like structure placed along this channel together with DNA.Another narrow space was recognizable between b and b^ユ subunits. Taking the affinity of b subunit to mRNA into account, this slit may be a channel for newly synthesizing mRNA.