The Primary Structure of Sensory Rhodopsin II: A Member of an Additional Retinal Protein Subgroup is Coexpressed with its Transducer, the Halobacterial Transducer of Rhodopsin II
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Media type:
E-Article
Title:
The Primary Structure of Sensory Rhodopsin II: A Member of an Additional Retinal Protein Subgroup is Coexpressed with its Transducer, the Halobacterial Transducer of Rhodopsin II
Published:
National Academy of Sciences of the United States of America, 1995
Published in:
Proceedings of the National Academy of Sciences of the United States of America, 92 (1995) 7, Seite 3036-3040
Language:
English
ISSN:
0027-8424
Origination:
Footnote:
Description:
The blue-light receptor genes (sopII) of sensory rhodopsin (SR) II were cloned from two species, the halophilic bacteria Haloarcula vallismortis (vSR-II) and Natronobacterium pharaonis (pSR-II). Upstream of both sopII gene loci, sequences corresponding to the halobacterial transducer of rhodopsin (Htr) II were recognized. In N. pharaonis, psopII and phtrII are transcribed as a single transcript. Comparison of the amino acid sequences of vHtr-II and pHtr-II with Htr-I and the chemotactic methyl-accepting proteins from Escherichia coli revealed considerable identities in the signal domain and methyl-accepting sites. Similarities with Htr-I in Halobacterium salinarium suggest a common principle in the phototaxis of extreme halophiles. Alignment of all known retinal protein sequences from Archaea identifies both SR-IIs as an additional subgroup of the family. Positions defining the retinal binding site are usually identical with the exception of Met-118 (numbering is according to the bacteriorhodopsin sequence), which might explain the typical blue color shift of SR-II to ≈490 nm. In archaeal retinal proteins, the function can be deduced from amino acids in positions 85 and 96. Proton pumps are characterized by Asp-85 and Asp-96; chloride pumps by Thr-85 and Ala-96; and sensors by Asp-85 and Tyr-96 or Phe-96.