Studies on calmodulin-binding proteins (CaMBPs) in the cilia of Tetrahymena

Abstract

As a first step to elucidate the involvement of calmodulin in Ca 2+-dependent regulation of ciliary motility, molecular species and properties of calmodulin-binding proteins (CaMBPs) in Tetrahymena cilia were investigated by a modified [ 125I]calmodulin overlay method. At least 36 kinds of CaMBPs were detected. All the CaMBPs bound to calmodulin in Ca 2+-dependent and calmodulin-specific manners, but they showed different Ca 2+-dependencies. Several of CaMBPs bound to calmodulin in the presence of 100 μM trifluoperazine, several did in the presence of 8 M urea, and a few of them were highly sensitive to trypsin digestion. Among these CaMBPs, we noticed a 95 000-dalton (D) CaMBP present in the outerdoublet microtubule fraction, which possessed some attributes of the calmodulin counterpart suggested from the results of our previous paper [12]. We discussed a possibility that this protein might correspond to one of the protein components Of the interdoublet link.