Phased A‐tracts bind to the α subunit of RNA polymerase with increased affinity at low temperature

Abstract
Previously we showed that the expression of a Clostridium perfringens phospholipase C gene (plc) is activated by promoter upstream phased A‐tracts in a low temperature‐dependent manner. In this paper we characterize the interaction between the α subunit of C. perfringens RNA polymerase and the phased A‐tracts. Hydroxyl radical footprinting and fluorescence polarization assaying revealed that the α subunit binds to the minor grooves of the phased A‐tracts through its C‐terminal domain with increased affinity at low temperature. The result provides a molecular mechanism underlying the activation of the plc promoter by the phased A‐tracts.