Tyrosine and carboxyl protonation changes in the bacteriorhodopsin photocycle. 1. M/sub 412/ and L/sub 550/ intermediates

Journal Article · Tue Oct 20 04:00:00 EDT 1987 · Biochemistry; (United States)

OSTI ID:5658009

Roepe, P; Herzfeld, J; Rothschild, K J

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), Journal Name: Biochemistry; (United States) Vol. 26:21; ISSN BICHA
• Country of Publication: United States
• Language: English

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59 BASIC BIOLOGICAL SCIENCES
AMINO ACIDS
BARYONS
CARBOXYLIC ACIDS
CHEMISTRY
DEUTERIUM COMPOUNDS
ELEMENTARY PARTICLES
EMISSION SPECTROSCOPY
FERMIONS
FOURIER TRANSFORM SPECTROMETERS
HADRONS
HYDROGEN COMPOUNDS
HYDROXY ACIDS
LABELLED COMPOUNDS
MEASURING INSTRUMENTS
MEMBRANES
NUCLEONS
ORGANIC ACIDS
ORGANIC COMPOUNDS
PH VALUE
PHOTOCHEMISTRY
PHOTOSYNTHETIC BACTERIA
PHOTOSYNTHETIC MEMBRANES
PIGMENTS
PROTEINS
PROTONS
REACTION INTERMEDIATES
RHODOPSIN
SPECTRA
SPECTROMETERS
SPECTROSCOPY
TEMPERATURE EFFECTS
TRITIUM COMPOUNDS
TYROSINE
ULTRAVIOLET SPECTRA