A transducer for microbial sensory rhodopsin that adopts GTG as a start codon is identified in Haloarcula marismortui

► The distance from the sensory rhodopsin (SR) to its cognate transducer is 0-3 bases. ► The transducer for the SRII is 1.4× longer than the transducer for the SRI. ► The transducer for the SR contains a two-transmembrane region in the N-terminal. ► The transducer for HmSRI is identified using alternative start codon GTG. ► The first RGB sensory system in haloarchaea is unique in Haloarcula marismortui.