Ca sup 2+ binding capacity of cytoplasmic proteins from rod photoreceptors is mainly due to arrestin

Journal Article · Tue Jun 05 00:00:00 EDT 1990 · Journal of Biological Chemistry; (USA)

OSTI ID:6719083

Huppertz, B; Weyand, I; Bauer, P J ^[1]

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1. Institut fuer Biologische Informationsverarbeitung, Forschungszentrum Juelich GmbH (Germany, F.R.)

Arrestin (also called S-antigen or 48-kDa protein) binds to photoexcited and phosphorylated rhodopsin and, thereby, blocks competitively the activation of transducin. Using Ca{sup 2+} titration in the presence of the indicator arsenazo III and {sup 45}Ca{sup 2+} autoradiography, we show that arrestin is a Ca2(+)-binding protein. The Ca{sup 2+} binding capacity of arresting-containing protein extracts from bovine rod outer segments is about twice as high as that of arrestin-depleted extracts. The difference in the Ca{sup 2+} binding of arrestin-containing and arrestin-depleted protein extracts was attributed to arrestin. Both, these difference-measurements of protein extracts and the measurements of purified arrestin yield dissociation constants for the Ca{sup 2+} binding of arrestin between 2 and 4 microM. The titration curves are consistent with a molar ratio of one Ca{sup 2+} binding site per arrestin. No Ca{sup 2+} binding in the micromolar range was found in extracts containing mainly transducin and cGMP-phosphodiesterase. Since arrestin is one of the most abundant proteins in rod photoreceptors occurring presumably up to millimolar concentrations in rod outer segments, we suggest that aside from its function to prevent the activation of transducin, arrestin acts probably as an intracellular Ca{sup 2+} buffer.

• OSTI ID: 6719083
• Journal Information: Journal of Biological Chemistry; (USA), Journal Name: Journal of Biological Chemistry; (USA) Vol. 265:16; ISSN JBCHA; ISSN 0021-9258
• Country of Publication: United States
• Language: English

Related Subjects

550201* -- Biochemistry-- Tracer Techniques
59 BASIC BIOLOGICAL SCIENCES
ALKALINE EARTH ISOTOPES
ALKALINE EARTH METAL COMPOUNDS
ANIMALS
ANTIGENS
AUTORADIOGRAPHY
BETA DECAY RADIOISOTOPES
BETA-MINUS DECAY RADIOISOTOPES
BIOCHEMICAL REACTION KINETICS
BIOCHEMISTRY
BODY
BODY AREAS
CALCIUM 45
CALCIUM COMPOUNDS
CALCIUM ISOTOPES
CATTLE
CELL CONSTITUENTS
CHEMISTRY
CHROMATOGRAPHY
CYTOPLASM
DAYS LIVING RADIOISOTOPES
DOMESTIC ANIMALS
ENZYMES
ESTERASES
EVEN-ODD NUCLEI
EYES
FACE
HEAD
HYDROLASES
INTERMEDIATE MASS NUCLEI
ISOTOPES
KINETICS
LIQUID COLUMN CHROMATOGRAPHY
MAMMALS
NUCLEI
ORGANIC COMPOUNDS
ORGANS
PHOSPHODIESTERASES
PROTEINS
RADIOISOTOPES
REACTION KINETICS
RUMINANTS
SENSE ORGANS
SEPARATION PROCESSES
VERTEBRATES