STRUCTURE AND FUNCTION OF MICROBIAL AND ANIMAL RHODOPSINS
The primary interests in our laboratory are the mechanisms by which photosensory receptors sense and transmit information concerning the color, intensity, and pattern of light in the environment. We study a widespread class of photoactive receptor proteins (rhodopsins) that consist of seven transmembrane helices connected by interhelical loops. The helices form a pocket for the photosensitive molecule vitamin-A aldehyde (retinal) that attaches in a covalent linkage to a lysine residue in the middle of the 7th helix buried in the core of the protein. These proteins are used for visual processes of various degrees of sophistication, ranging from detection of light-dark boundaries, light gradients, and light direction by single-cell microorganisms to high-resolution color image detection by higher animal eyes.
Photoisomerization of the retinylidene chromophore initiates a variety of types of signaling reactions. Mammalian visual pigments signal by binding and activating heterotrimeric G-proteins. Four distinctly different modes of signaling have been demonstrated for microbial rhodopsins: conformational coupling to bound membrane transducer subunits that relay signals to sensory pathways in the cytoplasm, binding to a cytoplasmic transducer, light-gated ion channel conduction, and light-regulated enzymatic activity encoded by the sensory rhodopsin protein. In addition, homologous microbial rhodopsins pumps drive active ion transport. Our laboratory studies in terms of structure/function how evolution has produced these distinctly different molecular functions from a shared protein scaffold.
UTHealth Medical School
Department of Biochemistry and Molecular Biology
Center for Membrane Biology
6431 Fannin Street, MSB 6.200
Houston, Texas 77030
713-500-5473 Direct 713-500-0652 Fax
Ph.D. - University of California, Berkeley
Jane Coffin Childs Postdoctoral Fellow - Harvard Medical School
Light sensors & photosensory transduction, Microbial rhodopsins, Membrane receptor structure/function, Optogenetics
Govorunova EG, Sineshchekov OA, Li H, Janz R, Spudich JL.
J Biol Chem. 2013 Oct 11;288(41):29911-22. doi: 10.1074/jbc.M113.505495. Epub 2013 Aug 30.
Ran T, Ozorowski G, Gao Y, Sineshchekov OA, Wang W, Spudich JL, Luecke H.
Acta Crystallogr D Biol Crystallogr. 2013 Oct;69(Pt 10):1965-80. doi: 10.1107/S0907444913017575. Epub 2013 Sep 20.
Govorunova EG, Sineshchekov OA, Janz R, Liu X, Spudich JL.
Science. 2015 Jun 25. pii: aaa7484. [Epub in Science Express ahead of print]