Low molecular weight microtubule-associated proteins are light chains of microtubule-associated protein 1 (MAP 1).

Abstract

Microtubule-associated protein 1 (MAP 1; MW = 350,000) was analyzed by column chromatography of microtubule protein obtained from calf brain gray and white matter. Two low MW proteins (LMW [low MW] MAP, MW 28,000 and 30,000) were found to cochromatograph with MAP 1 under all conditions examined. MAP 1 and LMW MAP were purified from calf brain white matter as a complex containing approximately equimolar amounts of the 2 spp. Urea (6 M) was used to remove the LMW MAP from MAP 1. Binding of MAP 1 to microtubules was unaffected by urea and occurred with or without the LMW species. EM of microtubules composed of purified tubulin and either MAP 1 preparation revealed that, like MAP 2, MAP 1 has the appearance of a filamentous arm on the microtubule surface.