Calmodulin-binding proteins within the slow phase of axonal transport in the rabbit vagus nerve

Calmodulin-binding proteins (CBPs) in the rabbit vagus nerve were studied by means of calmodulin-Sepharose affinity chromatography and polyacrylamide gel electrophoresis. The soluble fraction (10(5) g supernatant) of a nerve homogenate contained four CBPs with molecular weights of 44, 55, 91, and 93 kD, respectively. Slowly transported proteins were recovered in the vagus 3 days after injection of [35S]methionine into the nodose ganglion. Four labelled CBPs with molecular weights of 44, 55, 69, and 83 kD, respectively were found. The nodose ganglion contained two labelled CBPs, 44 and 55 kD. The 55-kD CBP was identified as tubulin after immunoblotting. In separate experiments it was also shown that bovine brain tubulin bound to the calmodulin column.