On the bioactive conformation of the rhodopsin chromophore: absolute sense of twist around the 6-s-cis bond.
Incubation of opsin with synthetic 6-s-locked retinoids 2a and 2b only led to pigment formation from the alpha-locked 2a, the CD spectrum of which was similar to that of native rhodopsin (Rh). This establishes that the 6-s-bond of the chromophore in rhodopsin is cis, and that its helicity is negative. Earlier cross-linking studies showed that the 11-cis to all-trans photoisomerization occurring in the batho-Rh to lumi-Rh conversion induces a flip over of the side carrying the ring moiety. The GTP-binding assay of pigment Rh-(2a), incorporating retinal analogue 2a, has shown that its activity is 80% that of the native pigment. That is, the overall conformation around the 6-s bond is retained in the steps leading to G-protein activation.
Fujimoto
Y
Y
Department of Chemistry, Columbia University, New York, NY 10027, USA.
Ishihara
J
J
Maki
S
S
Fujioka
N
N
Wang
T
T
Furuta
T
T
Fishkin
N
N
Borhan
B
B
Berova
N
N
Nakanishi
K
K
D000818:Animals; D002417:Cattle; D002942:Circular Dichroism; D008958:Models, Molecular; D011487:Protein Conformation; D017433:Protein Structure, Secondary; D012172:Retinaldehyde / Q000031:analogs & derivatives; D012243:Rhodopsin / Q000737:chemistry*; D017299:Rod Opsins / Q000737:chemistry; D013056:Spectrophotometry, Ultraviolet; D013237:Stereoisomerism
D017299:Rod Opsins; D012243:Rhodopsin; D012172:Retinaldehyde