Sensory Rhodopsins

The proteins:  sensory rhodopins are seven-helical transmembrane proteins related to the light-driven ion pump bacteriorhodospin (BR) which contain a retinal co-factor.  They are found in the archaea H. salinarum and N. pharaonis where they act as phototaxis receptors.  Sensory rhodopsin II (NpSRII) that mediates blue-light avoidance by the haloarchaeon Natronobacterium pharaonis.  The maximum absorption of the NpSRII all-trans chromophore is significantly blue-shifted with respect to BR (from 568 nm for BR to 497 nm for NpSRII).  This shift gives rise to the orange color (blue-light absorption) of the protein.  When a blue photon is absorbed by the NpSRII chromphore, rapid (pico second time scale) isomerization from all-trans to 13-cis,15-anti takes place.  This light-induced shape change of the chromophore in turn causes the surrounding protein to also change shape.  This change in chape is ultimately sensed by the specific transducer protein called HtrII, which binds tightly to NpSRII.   HtrII then signals to the ???? [under construction]

The crystals:  the crystals are grown from cubic lipid phase (Landau & Rosenbusch, PNAS, 1996) and form long orange needles:

NpSRII crystal in cryo-loop at ESRF ID13

Fig. 1:  NpSRII crystal in cryo loop at ESRF microfocus beamline ID13

The paper:

Crystal Structure of Sensory Rhodopsin II at 2.4 Å:  Insights into Color Tuning and Transducer Interaction.
H Luecke, B Schobert, JK Lanyi, EN Spudich, JL Spudich (2001) Science July 12, 2001.

The atomic model:

1jgj.pdb (released July 12, 2001): 2.4 Å wild-type structure described in the 2001 Science paper.