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Asp 85 is the only internal aspartic acid that gets protonated in the M intermediate and the purple‐to‐blue transition of bacteriorhodopsin A solid‐state 13 C CP‐MAS NMR investigation
Author(s) -
G. Metz,
Friedrich Siebert,
Martin Engelhard
Publication year - 1992
Publication title -
febs letters
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.593
H-Index - 257
eISSN - 1873-3468
pISSN - 0014-5793
DOI - 10.1016/0014-5793(92)80528-o
Subject(s) - protonation , aspartic acid , bacteriorhodopsin , chemistry , stereochemistry , crystallography , biochemistry , amino acid , organic chemistry , membrane , ion
High‐resolution solid‐state 13 C NMR spectra of the ground state and M intermediate of the bacteriorhodopsin mutant D 96 N with the isotope label at [4‐ 13 C]Asp and [11‐ 13 C]Trp were recorded. The NMR spectra show that Asp 85 is protonated in the M intermediate. The environment of Asp 85 is quite hydrophobic. On the other hand, Asp 212 remains deprotonated and a slight shift to lower field indicates a more hydrophilic environment. Asp 85 also protonates in the purple‐to‐blue transition or 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.