Functional analysis of the major outer membrane protein gene promoters of Chlamydia trachomatis.

We determined that the putative upstream promoter of the long transcript (P1) of ompA, the gene encoding the major outer membrane protein of Chlamydia trachomatis L2, is recognized in vitro by the major sigma factor of chlamydiae, sigma 66. We found no evidence that the putative downstream promoter of the short ompA transcript (P1) is functional in vitro. RNase protection of guanylyltransferase-capped transcripts made in vivo confirmed that P2 is a primary transcript while P1 is a processed product of a longer transcript, possibly P2.