Asp85 is the only internal aspartic acid that gets protonated in the M intermediate and the purple-to-blue transition of bacteriorhodopsin. A solid-state 13C CP-MAS NMR investigation.
High-resolution solid-state 13C NMR spectra of the ground state and M intermediate of the bacteriorhodopsin mutant D96N with the isotope label at [4-13C]Asp and [11-13C]Trp were recorded. The NMR spectra show that Asp85 is protonated in the M intermediate. The environment of Asp85 is quite hydrophobic. On the other hand, Asp212 remains deprotonated and a slight shift to lower field indicates a more hydrophilic environment. Asp85 also protonates in the purple-to-blue transition of bacteriorhodopsin in the deionized membrane, where it experiences a similar environment to M. The shift of Trp resonances in M reflect a conformational change of the protein in forming the M intermediate.
Metz
G
G
Institut für Biophysik und Strahlenbiologie der Universität, Freiburg, Germany.
Siebert
F
F
Engelhard
M
M
D001224:Aspartic Acid / Q000737:chemistry*; D001436:Bacteriorhodopsins / Q000737:chemistry* / Q000235:genetics; D006217:Halobacterium / Q000235:genetics / Q000378:metabolism; D009682:Magnetic Resonance Spectroscopy; D009154:Mutation; D011487:Protein Conformation; D011522:Protons
D011522:Protons; D001224:Aspartic Acid; D001436:Bacteriorhodopsins