NOVEL BACTERIAL RHODOPSINS FROM HALOARCULA-VALLISMORTIS

New bacterial rhodopsins of the cruxrhodopsin (cR) tribe were identifi ed in a type strain Haloarcula vallismortis. The genes encoding a bact eriorhodopsin-like ion pump (named cR-3), a halorhodopsin-like ion pum p (chR-3) and a sensor rhodopsin (csR-3) were cloned and sequenced. To gether with the data for vsRII (Seidel et al., Proc. Natl. Acad. Sci. USA 92, 3036-3040 (1995); cpR-3 in our notation), the primary structur es of a set of four rhodopsins are now all known only in this species, They are separated by almost the same distances in homology, suggesti ng that they have derived from a single ancestral rhodopsin. The degre e of conservation in the amino acid sequence of each helix showed that helices C and G are relatively well conserved in all rhodopsins, wher eas helices DEF are conserved especially in sensor rhodopsin-I, possib ly because these helices are needed for interaction with the transduce r protein (Htr). (C) 1996 Academic Press, Inc.