Characterization and sequence of a plasmid from the trachoma biovar of Chlamydia trachomatis

The 7.5-kb plasmid of Chlamydia trachomatis, trachoma biovar, was mapped for restriction enzyme sites and sequenced. The complete nucleotide sequence, the first reported for any chlamydial plasmid, revealed nine open reading frames which could code for polypeptides greater than 10 kDa. These putative polypeptides contain 35-47% hydrophobic amino acid residues. Two putative polypeptides of 30 kDa are highly basic and one of 23 kDa is acidic. A region composed of four 22-bp repeats, AT-rich clusters, an inverted repeat, and a 30-kDa basic protein is similar in organization to the origins of replication in a number of Escherichia coli plasmids. Northern blot analysis of the plasmid RNA showed transcripts longer than the length of the plasmid, suggesting a single transcription initiation signal.