DNA structure and novel amino and carboxyl termini of the Chlamydia sigma 70 analogue modulate promoter recognition.

Genes from the eubacterium Chlamydia typically do not share promoter consensus sequences with those of Escherichia coli and are not expressed when cloned in E. coli; nevertheless, the major sigma-subunit identified from Chlamydia trachomatis has nearly identical amino acid sequence to E. coli sigma 70 in regions that contact DNA. Following expression of the chlamydial sigma-subunit gene in E. coli, expression was specifically initiated from chlamydial promoter regions. Selective recognition of chlamydial promoters by holoenzyme was dependent upon the structure of the promoter DNA coupled with novel amino- and carboxyl-terminal extensions of the chlamydial sigma-subunit.