A tubulin identified by a monoclonal antibody is not present in mitotic spindles

A monoclonal antibody, G8, which recognizes a form of tubulin (G8-tubulin) with a novel distribution in Rat-1 cells and Potorous tridactylis kidney (Ptk-2) cells was isolated. G8 labeled the interphase cytoskeleton of Rat-1 fibroblasts but not mitotic spindles or midbodies. G8 also stained a fiber network in some but not all Ptk-2 interphase cells but did not label mitotic spindles or midbodies in these cells. G8-tubulin is the only identified tubulin known to be absent from these structures. This distribution may indicate that G8-tubulin possesses functional specificity.