Tyrosine and carboxyl protonation changes in the bacteriorhodopsin photocycle. 1. M/sub 412/ and L/sub 550/ intermediates
The role of tyrosines in the bacteriorhodopsin (bR) photocycle has been investigated by using Fourier transform infrared (FTIR) and UV difference spectroscopies. Tyrosine contributions to the BR/sub 570/ ..-->.. M/sub 412/ FTIR difference spectra recorded at several temperatures and pH's were identified by isotopically labeling tyrosine residues in bacteriorhodopsin. The frequencies and deuterium/hydrogen exchange sensitivities of these peaks and of peaks in spectra of model compounds in several environments suggest that at least two different tyrosine groups participate in the bR photocycle during the formation of M/sub 412/. One group undergoes a tyrosinate ..-->.. tyrosine conversion during the BR/sub 570/ ..-->.. K/sub 630/ transition. A second tyrosine group deprotonates between L/sub 550/ and M/sub 412/. Low-temperature UV difference spectra in the 220-350-nm region of both purple membrane suspensions and rehydrated films support these conclusions. The UV spectra also indicate perturbations(s) of one or more tryptophan group(s). Several carboxyl groups appear to undergo a series of protonation changes between BR/sub 570/ and M/sub 412/, as indicated by infrared absorption changes in the 1770-1720-cm/sup -1/ region. These results are consistent with the existence of a proton wire in bacteriorhodopsin that involves both tyrosine and carboxyl groups.
- Research Organization:
- Boston Univ., MA
- OSTI ID:
- 5658009
- Journal Information:
- Biochemistry; (United States), Vol. 26:21
- Country of Publication:
- United States
- Language:
- English
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59 BASIC BIOLOGICAL SCIENCES
REACTION INTERMEDIATES
EMISSION SPECTROSCOPY
RHODOPSIN
PHOTOCHEMISTRY
DEUTERIUM COMPOUNDS
FOURIER TRANSFORM SPECTROMETERS
PH VALUE
PHOTOSYNTHETIC BACTERIA
PHOTOSYNTHETIC MEMBRANES
PROTONS
TEMPERATURE EFFECTS
TRITIUM COMPOUNDS
TYROSINE
ULTRAVIOLET SPECTRA
AMINO ACIDS
BARYONS
CARBOXYLIC ACIDS
CHEMISTRY
ELEMENTARY PARTICLES
FERMIONS
HADRONS
HYDROGEN COMPOUNDS
HYDROXY ACIDS
LABELLED COMPOUNDS
MEASURING INSTRUMENTS
MEMBRANES
NUCLEONS
ORGANIC ACIDS
ORGANIC COMPOUNDS
PIGMENTS
PROTEINS
SPECTRA
SPECTROMETERS
SPECTROSCOPY
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