THE ULTRAVIOLET FLUORESCENCE OF BACTERIORHODOPSIN AND THE LOCATION OF TRYPTOPHANYL RESIDUES |
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Authors: | Warren V Sherman |
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Institution: | Department of Physical Sciences, Chicago State University, Chicago, IL 60628, USA |
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Abstract: | Abstract— The ultraviolet fluorescence spectrum of bacteriorhodopsin is characterized by emission from an ensemble of internal, surface and exposed Trp residues. The temperature dependence of fluorescence yields exhibits a discontinuity at about 30°C coincident with previously observed transitions in membrane lipid microviscosity, photocycle lifetime and photoconductivity. Quenching at high pH coincides with ionization of Tyr and an emission red shift to a spectrum typical of that of tyrosinate. Guanidine hydrochloride produces only partial protein denaturation, increasing the number of exposed Trp by 50%. While exposed Trp in native bacteriorhodopsin are in the minority, they represent a higher proportion of total Trp than is found in rhodopsin of animal rod outer sections. |
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