High levels of a heat-labile calmodulin-binding protein (CaM-BP80) in bovine neostriatum

Abstract
Bovine brain contains a heat-labile, 80,000 dalton calmodulin-binding protein (CaM-BP80) which inhibits the calmodulin-dependent activities of cyclic 3'',5''-nucleotide phosphodiesterase, adenylate cyclase and Ca2+-ATPase in vitro. CaM-BP80 is composed of 2 polypeptides (60,000 and 18,500 daltons) present in a 1:1 ratio. An antibody directed against CaM-BP80 was raised in rabbits and a radioimmunoassay [RIA] was developed, having a sensitivity of 60 fmol of CaM-BP80. Using the RIA, the levels of CaM-BP80 in various bovine tissues were determined. The protein was found primarily in the brain, present in particularly high levels in the neostriatum. These results, together with immunohistochemical localization of CaM-BP80 at the postsynaptic densities and the microtubules of postsynaptic dendrites suggest that the protein may have a role in the cerebrum at the site of neurotransmitter action and at the level of microtubular function.

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