Sequence comparison of Heterosigma akashiwo Trg1 with select bacterial response regulators. The Heterosigma akashiwo Trg1 sequence (accession number CAB46638) was aligned with Escherichia coli PhoB (P03025), E. coli OmpR (P08402) and Thermotoga maritima OmpR (1KGSA). Receiver and DNA binding domains are underlined and overlined, respectively. Within the receiver domain, the phosphorylation site is indicated by an asterisk (*). Within the DNA binding domain, the RNA polymerase binding site (α2-α3 loop) is boxed and bolded.