title: A transducer for microbial sensory rhodopsin that adopts GTG as a start codon is identified in Haloarcula marismortui.
abstract: Microbial sensory rhodopsins are known to mediate phototaxis, and all of the known sensory rhodopsins execute this function with a specific cognate transducer that has two-transmembrane (2-TM) regions. In the genome of Haloarcula marismortui, a total of six rhodopsin genes were annotated, and we previously showed three of them to be the ion type and suggested the other three as sensory type, even though the candidate transducer gene, htr, for HmSRI was missing the 2-TM region that is found in all of the other known transducers. Here we showed this htr gene featured a preceding 2-TM region when the alternative start codon GTG located 291 nucleotides upstream of the original annotated open reading frame (ORF) was introduced and it is named as htrI in this study. Overexpression of HmHtrI exhibited it existed as a membrane protein and several biophysical assays confirmed it functionally interacted with HmSRI. Together with our previous reverse-transcriptase-PCR results and phototaxis measurements, the new ORF of original predicted soluble htr gene product was a membrane protein with a 2-TM region, HmHtrI; and it serves as the cognate transducer for HmSRI. HmHtrI therefore is the first transducer for the sensory rhodopsin adopted start codon other than ATG.
authors.affiliation: Department of Biochemical Science and Technology, College of Life Science, National Taiwan University, 1, Roosevelt Rd., Sec. 4, 10617 Taipei, Taiwan. d97b47403@ntu.edu.tw
authors.forename: Hsu-Yuan
authors.initials: HY
authors.lastname: Fu
authors.forename: Yen-Hsu
authors.initials: YH
authors.lastname: Lu
authors.forename: Hsiu-Ping
authors.initials: HP
authors.lastname: Yi
authors.forename: Chii-Shen
authors.initials: CS
authors.lastname: Yang
mesh_terms: D000595:Amino Acid Sequence; D018387:Codon, Initiator / Q000235:genetics*; D019295:Computational Biology; D004926:Escherichia coli / Q000235:genetics; D019614:Haloarcula marismortui / Q000235:genetics*; D006863:Hydrogen-Ion Concentration; D008969:Molecular Sequence Data; D055355:Opsins / Q000235:genetics; D025603:Sensory Rhodopsins / Q000235:genetics*; D016415:Sequence Alignment; D015398:Signal Transduction
chemical_list: D018387:Codon, Initiator; D055355:Opsins; D025603:Sensory Rhodopsins