Medizinische Universität Graz Austria/Österreich - Forschungsportal - Medical University of Graz
Gewählte Publikation:
Huppertz, B; Weyand, I; Bauer, PJ.
Ca2+ binding capacity of cytoplasmic proteins from rod photoreceptors is mainly due to arrestin.
J Biol Chem. 1990; 265(16):9470-9475
Doi: 10.1016/S0021-9258(19)38873-8
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- Führende Autor*innen der Med Uni Graz
- Huppertz Berthold
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- Abstract:
- Arrestin (also called S-antigen or 48-kDa protein) binds to photoexcited and phosphorylated rhodopsin and, thereby, blocks competitively the activation of transducin. Using Ca2+ titration in the presence of the indicator arsenazo III and 45Ca2+ autoradiography, we show that arrestin is a Ca2(+)-binding protein. The Ca2+ 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 Ca2+ 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 Ca2+ binding of arrestin between 2 and 4 microM. The titration curves are consistent with a molar ratio of one Ca2+ binding site per arrestin. No Ca2+ 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 Ca2+ buffer.
- Find related publications in this database (using NLM MeSH Indexing)
- 3',5'-Cyclic-GMP Phosphodiesterase - metabolism
- Animals - metabolism
- Antigens - isolation and purification
- Arrestin - isolation and purification
- Arsenazo III - isolation and purification
- Autoradiography - isolation and purification
- Calcium - metabolism
- Calcium Radioisotopes - metabolism
- Calcium-Binding Proteins - metabolism
- Cattle - metabolism
- Chromatography, High Pressure Liquid - metabolism
- Cytoplasm - analysis
- Darkness - analysis
- Eye Proteins - isolation and purification
- Light - isolation and purification
- Osmolar Concentration - isolation and purification
- Photoreceptors - analysis
- Research Support, Non-U.S. Gov't - analysis
- Rod Outer Segments - analysis
- Transducin - metabolism