Conformational Changes in Bacteriorhodopsin Accompanying Ionophore Activity

Conference · Sun May 01 04:00:00 EDT 1977

OSTI ID:5335668

Packer, Lester ^[1]; Konishi, Tetsuya ^[1]; Shieh, Paul ^[1]

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1. University of California, Berkeley, CA (United States); Lawrence Berkeley Laboratory (LBL), Berkeley, CA (United States)

We conclude from planar membrane and liposome studies with bacteriorhodopsin in purple membrane fragments that the activity of bacteriorhodopsin in the purple membrane is increased, as judged by greater photopotentials across planar membranes or proton translocation in liposomes, by cations particularly bivalent cations as Ca⁺⁺, and by applied electric fields. The effect of bivalent ions appears to be two-fold, a direct effect on BR oriented in different directions and promoting interaction of liposomes at the planar membrane interface. Applied electrical fields appear to affect orientation of purple membranes at the planar membrane interface. Polymer stabilized black lipid membranes will prove quite useful for extending this test system for the study of ionophore activity of biological catalysts. Bacteriorhodopsin in the purple membrane patch exhibits considerable thermal stability and this intrinsic stability is enhanced by treatment with bifunctional crosslinking reagents. After chemical modification of bacteriorhodopsin in the light- or dark-adapted state, differences in proton pump activity are found in BR liposomes (which are consistent with differences in the number of remaining free lysine and tryptophan residues). These results indicate that two conformational states of the protein of bacteriorhodopsin are involved in its functioning as an ionophore. Studies with bifunctional crosslinking reagents having a defined chain length, indicate that the proton is transferred through a channel and/or pore present in the interior of the bacteriorhodopsin molecule rather than by a translocation mechanism.

• Research Organization: University of California, Berkeley, CA (United States); Lawrence Berkeley Laboratory (LBL), Berkeley, CA (United States)
• Sponsoring Organization: US Energy Research and Development Administration (ERDA)
• DOE Contract Number: W-7405-ENG-48
• OSTI ID: 5335668
• Report Number(s): LBL--6389; CONF-7606166-1
• Country of Publication: United States
• Language: English

Related Subjects

550200* -- Biochemistry
550500 -- Metabolism
59 BASIC BIOLOGICAL SCIENCES
BACTERIA
BARYONS
BIOCHEMICAL REACTION KINETICS
CATIONS
CHARGED PARTICLES
CONFIGURATION INTERACTION
ELECTRIC FIELDS
ELEMENTARY PARTICLES
FERMIONS
HADRONS
IONS
KINETICS
MEMBRANES
METABOLISM
MICROORGANISMS
NUCLEONS
PIGMENTS
PROTONS
REACTION KINETICS
STRUCTURAL CHEMICAL ANALYSIS