CALBINDIN(28KDA) (CALRETININ) ARE SUBSTANTIALLY LOCALIZED IN AND CALBINDIN(30KDA) THE PARTICULATE FRACTION OF RAT-BRAIN

Calbindin(28kDa) is implicated in cytosolic calcium transport and calc ioprotection functions, principally as a mobile calcium buffer. Using immunoblotting, we have found that 36% of total calbindin(28kDa) is in the particulate fraction of rat brain. Particulate calbindin(28kDa) w as located both within and outside organelles and required detergent f or solubilisation. Equivalent observations were made for calbindin(30k Da), 27% of which was insoluble. These findings indicate that a substa ntial proportion of calbindin does not function as a mobile calcium bu ffer, and perhaps instead has a calcium signalling role through target ligands in the insoluble cellular fraction.