Crystal Structure of the 13-cis Isomer of Bacteriorhodopsin in the Dark-adapted State

Bistable Retinal Schiff Base Photodynamics of Histidine Kinase Rhodopsin HKR1 from Chlamydomonas reinhardtii

“…Thermal equilibration between ground‐state isoforms occurs also for other microbial rhodopsins. In dark‐adapted bacteriorhodopsin the ratio of all‐ trans retinal to 13‐ cis ,15‐ syn retinal is 1:1 to 1:2 . Using 13 C NMR spectroscopy it was determined that dark‐adapted bacteriorhodopsin contains all‐ trans ,15‐ anti and 13‐ cis ,15‐ syn isomers in a ratio of 1:1.5 .…”

Crystal Structures of Archaerhodopsin-1 and -2: Common Structural Motif in Archaeal Light-driven Proton Pumps

“…This observation is in accordance with the previous argument that these residues are absolutely required for fixation of the C5-C12 portion of the polyene chain and thus for donating the stereospecificity of the retinal isomerization. 10 However, a residue (Met145 in aR-1 and bR) contacting the C5 methyl of retinal is substituted to phenylalanine in aR-2. 3 Since the side-chain of Met145 pushes the ionone ring downwards, the retinal polyene chain of the all-trans retinal is bent largely in aR-1 or bR.…”

“…[10][11][12][13][14][15][16] More recently, retinal proteins with the same photochemical property as archaeal rhodopsins have been shown to exist in eubacteria and uni-cell eukaryotes. [17][18][19] Structural and functional comparisons of these retinal proteins have widened our understanding as to how a prototype rhodopsin had evolved to acquire different functions.…”

Crystal Structures of Different Substates of Bacteriorhodopsin's M Intermediate at Various pH Levels

“…[6][7][8][9][18][19][20][21][22][23][24][25][26][27][28] It is not necessarily the case that the same conformational change is induced in the different crystal forms. Crystallographic studies of the P622 crystal have shown that the following structural changes take place during the proton pumping cycle: 9,21,23 (1) in the L intermediate, the Schiff base NH bond is directed toward the extracellular side and interacts with a water molecule that is relocated to an open space generated by rotation of the side chain of Leu93; (2) in the L/M equilibrium state generated at 200 K, mechanical stress in the retinal-Ly216 chain is released by deformation of the main chain of Lys216, causing a significant reduction in the pK a value of the Schiff base and thereby initiating partial proton transfer to Asp85; and (3) complete proton transfer to Asp85 is established when the proton release pathway undergoes a large structural change, including disruption of the paired structure in PRC.…”