Comparison of the microtubule formation induced by cytosynalin and MAPs

A comparison was made of cytosynalin- and MAPs-induced microtubule formation. Cytosynalin (a 35 kDa cytoskeleton-interacting and calmodulin-binding protein) facilitated more rapid and extensive microtubule formation than MAPs. Electron microscopic examination revealed that the cytosynalin-induced microtubules were 24 nm tubules surrounded by a periodic nap structure along their length. Consequently, the apparent diameter of microtubules was seen as 34 nm. Cytosynalin maximally bound to tubulin dimer at a molar ratio of 1:1. The effect of cytosynalin on the microtubule formation was found to be more potent than that of MAP2 or tau factor as determined by electron microscopy and cosedimentation assay.