Identification of distinct domains for signaling and receptor interaction of the sensory rhodopsin I transducer, HtrI.
The phototaxis-deficient mutant of Halobacterium salinarium, Pho81, lacks both sensory rhodopsin I (SR-I) and its putative transducer protein HtrI, according to immunoblotting and spectroscopic criteria. From restriction analysis and selected DNA sequencing, we have determined that the SR-I- HtrI- phenotype results from an insertion of a 520-bp transposable element, ISH2, into the coding region of the SR-I apoprotein gene sopI and deletion of 11 kbp upstream of ISH2 including the first 164 bp of sopI and the entire htrI gene. SR-I and HtrI expression as well as full phototaxis sensitivity are restored by transformation with a halobacterial plasmid carrying the htrI-sopI gene pair and their upstream promoter region. An internal deletion of a portion of htrI encoding the putative methylation and signaling domains of HtrI (253 residues) prevents the restoration of phototaxis, providing further evidence for the role of HtrI as a transducer for SR-I. Analysis of flash-induced photochemical reactions of SR-I over a range of pH shows that the partially deleted HtrI maintains SR-I interactions sites responsible for modulation of the SR-I photocycle.
Department of Microbiology and Molecular Genetics, University of Texas Medical School Health Science Center, Houston 77030.
V J
VJ
Yao
E N
EN
Spudich
J L
JL
Spudich
D000907:Antibodies, Bacterial; D019843:Archaeal Proteins; D001426:Bacterial Proteins / Q000096:biosynthesis / Q000235:genetics* / Q000276:immunology; D001436:Bacteriorhodopsins / Q000235:genetics*; D001483:Base Sequence; D002465:Cell Movement / Q000235:genetics*; D004252:DNA Mutational Analysis; D004926:Escherichia coli / Q000235:genetics; D006217:Halobacterium / Q000235:genetics* / Q000528:radiation effects; D025602:Halorhodopsins; D008027:Light; D008565:Membrane Proteins / Q000096:biosynthesis / Q000235:genetics* / Q000276:immunology; D008969:Molecular Sequence Data; D011994:Recombinant Proteins / Q000096:biosynthesis; D025603:Sensory Rhodopsins; D015398:Signal Transduction / Q000235:genetics*; D013329:Structure-Activity Relationship; D014170:Transformation, Genetic
D000907:Antibodies, Bacterial; D019843:Archaeal Proteins; D001426:Bacterial Proteins; D025602:Halorhodopsins; D008565:Membrane Proteins; D011994:Recombinant Proteins; C061497:SRI protein, Halobacterium; D025603:Sensory Rhodopsins; C082504:htrI protein, Halobacterium salinarium; D001436:Bacteriorhodopsins