Comparison of the microtubule proteins of neuroblastoma cells, brain, and Chlamydomonas flagella.

Intact A microtubules isolated from outer doublet microtubules of Chlamydomonas flagella contain two separable proteins (tubulins) that differ in molecular weight and in amino-acid composition. The microtubule protein isolated from brain or neuroblastoma cells also has two electrophoretically distinct tubulins. Although the two tubulins of brain and neuroblastoma cells are electrophoretically similar to each other, only one of these tubulins migrates with the flagellar tubulins. This is the first evidence that (a) isolated, morphologically intact, single microtubules from flagella contain at least two different tubulins, and (b) at least one of these tubulins differs from tubulins that are isolated from other sources.