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. Author manuscript; available in PMC: 2014 Dec 1.
Published in final edited form as: Amino Acids. 2013 Sep 20;45(6):10.1007/s00726-013-1593-y. doi: 10.1007/s00726-013-1593-y

Fig. 4.

Fig. 4

Asymmetry of activated rhodopsin (Rho*) dimer within rhodopsin-Gt (Rho*-Gt) complex. Gt binds to fully light activated rhodopsin (Rho) forming the Rho*-Gt complex. After light illumination, 11-cis-retinal (11-cis-RAL) of ground state rhodopsin (shown as red-red dimer) isomerizes to all-trans-retinal (all-trans-RAL) (yellow-yellow dimer) allowing binding of the Gt heterotrimer (Gtα is depicted in salmon, Gtβ in green and Gtγ in light blue). This binding prevents chromophore release from one rhodopsin in the dimer, introducing dimer asymmetry in the Rho*-Gt complex (shown as a yellow-grey dimer bound to Gt and black trace on the chromatogram). a, retinal-free rhodopsin molecule of the Rho*-Gt complex can be regenerated with 9-cis-retinal (9-cis-RAL) (shown as yellow-pink rhodopsin dimer bound to Gt and blue trays on the chromatogram). Release of chromophore from the Gt-protected rhodopsin molecule can be promoted by NH2OH, resulting then in formation of an asymmetric retinal free and 9-cis-retinal regenerated rhodopsin dimer complexed to Gt (shown as grey-pink rhodopsin dimer bound to Gt and dark cyan trace on the chromatogram). Regeneration of this complex with 11-cis-retinal surprisingly results in formation of all-trans-retinal bound and 9-cis-retinal bound asymmetric rhodopsin dimer in the complex with Gt (shown as yellow-pink rhodopsin dimer bound to Gt and cyan trace on the chromatogram). b, the chromophore-free Rho*-Gt complex (modeled as a grey-grey rhodopsin dimer bound to Gt and black lane on the chromatogram) can be generated by treatment of the Rho*-Gt complex with NH2OH. Then this chromophore-free Rho*-Gt complex can be regenerated with 9-cis-retinal which binds to both rhodopsin monomers within the dimer (shown as a pink-pink dimer bound to Gt and dark green trace on the chromatogram). Alternatively, it can be regenerated with all-trans-retinal but only one rhodopsin molecule, the one directly coupled to Gt binds all-trans-retinal (shown as a yellow-grey dimer bound to Gt and light green trace on the chromatogram).