The structures of the active center in dark-adapted bacteriorhodopsin by solution-state NMR spectroscopyPatzelt, H., Simon, B., Ter Laak, A., Kessler, B., Kuhne, R., Schmieder, P., Oesterhaelt, D., Oschkinat, H.
(2002) Proc.Natl.Acad.Sci.USA 99: 9765-9770
- PubMed: 12119389
- DOI: 10.1073/pnas.132253899
- Primary Citation of Related Structures:  1R2N
- PubMed Abstract:
The two forms of bacteriorhodopsin present in the dark-adapted state, containing either all-trans or 13-cis,15-syn retinal, were examined by using solution state NMR, and their structures were determined. Comparison of the all-trans and the 13-cis,15 ...
The two forms of bacteriorhodopsin present in the dark-adapted state, containing either all-trans or 13-cis,15-syn retinal, were examined by using solution state NMR, and their structures were determined. Comparison of the all-trans and the 13-cis,15-syn forms shows a shift in position of about 0.25 A within the pocket of the protein. Comparing this to the 13-cis,15-anti chromophore of the catalytic cycle M-intermediate structure, the 13-cis,15-syn form demonstrates a less pronounced up-tilt of the retinal C12[bond]C14 region, while leaving W182 and T178 essentially unchanged. The N[bond]H dipole of the Schiff base orients toward the extracellular side in both forms, however, it reorients toward the intracellular side in the 13-cis,15-anti configuration to form the catalytic M-intermediate. Thus, the change of the N[bond]H dipole is considered primarily responsible for energy storage, conformation changes of the protein, and the deprotonation of the Schiff base. The structural similarity of the all-trans and 13-cis,15-syn forms is taken as strong evidence for the ion dipole dragging model by which proton (hydroxide ion) translocation follows the change of the dipole.
Max-Planck-Institut für Biochemie, Abteilung Membranbiochemie, Am Klopferspitz 18a, 82152 Martinsried, Germany;.