Calcium ion-gated proton fluxes in choroplast thylakoid membranes
Replacement of sucrose by 100 mM KCl in the choroplast thylakoid storage media, shifts proton gradients in thylakoids from a localized to a delocalized mode of energy coupling. This conversion appears to be regulated by Ca{sup 2+} ions. Addition of divalent cations to the KCl containing medium maintained thylakoids in a localized coupling response. Inclusion of lipid soluble Ca{sup 2+} chelators to sucrose stored thylakoids normally displaying localized coupling behavior, resulted in a conversion to a delocalized pattern typical of KCl stored thylakoids. The Ca{sup 2+} antagonists directed towards calmodulin, chorpromazine and trifluoperazine, perturb the H{sup +} gating function in a way consistent with the Ca{sup 2+} gating action, involving a membrane protein analogous to a calmodulin-Ca{sup 2+} complex functioning as the closed gate structure. Chlorpromazine bound at the Ca{sup 2+} occupied sites causes partial blockage of the proton flux between the membrane domains and the lumen. ({sup 3}H)Chlorpromazine used as a photoaffinity probe, identified four membrane proteins of Mr 7-14 kDa, as possibly being part of the gating function. One of the proteins was identified as the 8 kDa CF{sub 0} subunit by its N-terminus amino acid sequence analysis of co-labeling with ({sup 14}C)DCCD. A 6 kDa protein also bound ({sup 3}H)CPZ similarly, from which a 10 amino acid peptide sequence was determined. This polypeptide may be part of a yet unidentified protein involved in the gating mechanism.
- Research Organization:
- Purdue Univ., Lafayette, IN (USA)
- OSTI ID:
- 6073024
- Resource Relation:
- Other Information: Thesis (Ph. D.)
- Country of Publication:
- United States
- Language:
- English
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Related Subjects
CALCIUM COMPOUNDS
BIOLOGICAL FUNCTIONS
PROTONS
MEMBRANE TRANSPORT
AMINO ACID SEQUENCE
CARBON 14 COMPOUNDS
CATIONS
CHLOROPLASTS
PHOTOSYNTHETIC MEMBRANES
THYLAKOID MEMBRANE PROTEINS
TRACER TECHNIQUES
TRITIUM COMPOUNDS
ALKALINE EARTH METAL COMPOUNDS
BARYONS
CELL CONSTITUENTS
CHARGED PARTICLES
ELEMENTARY PARTICLES
FERMIONS
FUNCTIONS
HADRONS
HYDROGEN COMPOUNDS
IONS
ISOTOPE APPLICATIONS
LABELLED COMPOUNDS
MEMBRANE PROTEINS
MEMBRANES
MOLECULAR STRUCTURE
NUCLEONS
ORGANIC COMPOUNDS
PROTEINS
550201* - Biochemistry- Tracer Techniques