The relationship between the chromophore moiety and the cation binding sites in bacteriorhodopsin |
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Authors: | Mireia Duñach Michel Seigneuret Jean-Louis Rigaud Esteve Padrós |
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Institution: | (1) Unitat de Biofisica, Department de Bioquimica i Biologia Molecular, Facultat de Medicina, Universitat Autonoma de Barcelona, 08193 Bellaterra, Barcelona, Spain;(2) Départment de Biologie Service de Biophysique, Centre d'Etudes Nucléaires de Saclay, 91191 Gif-wur-Yvette Cedex, France |
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Abstract: | Bleaching of the purple membrane strongly reduces the number of divalent cation binding sites as well as their affinities. Conversely, deionization of the bleached membrane drastically inhibits the chromophore regeneration. Proteolysis experiments using bromelain show that the bleached membrane has an additional cleavage site probably located at the fifth loop, whereas in the blue membrane, the C-terminal tail is no longer susceptible to proteolysis. It is suggested that there exists a close relationship between the retinal environment and one or more of the cation binding sites. |
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Keywords: | bacteriorhodopsin retinal cation binding sites proteolysis bleached membrane |
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