PNNL

Abstract

Chlamydia trachomatis is a bacterial obligate intracellular parasite and a significant cause of human disease, including sexually transmitted infections. The RNA polymerase binding protein DksA functions as a transcription factor in bacteria and the genome of C. trachomatis encodes a protein annotated to be a DksA ortholog (DksACt). DksACt expression is dynamic with maximal expression induced at 15-20 hours post infection, a time frame correlating with the onset of Reticulate Body (RB) to Elementary Body (EB) transitions. Ectopic overexpression of DksACt prior to RB-EB transitions in C. trachomatis-infected HeLa cells resulted in a glucose-dependent shift in recovered infectious progeny where incubation of host cells in 0.25 mM glucose increased recovered EBs by 66% while incubation of host cells in 1 or 5 mM glucose decreased recovered EBs by 26% and 43%, respectively. These findings are consistent with a role for DksACt in regulation of chlamydial responses to nutrient availability and EB generation. DksACt did not functionally complement the prototypical variant of Escherichia coli (DksAEc). Structural analysis revealed that the topology of DksACt is similar to DksAEc with the most significant difference in the E27-V62 region of the coiled-coil domain where no electron density was observed, suggesting this region is intrinsically variable.