Strongly basic polypeptides among microtubule associated proteins

Isoelectrofocussing between pH 3.5 and 9.5, or 9 and 11 in the first direction of two-dimensional gel electrophoreses reveal that the bands of microtubule associated proteins, e.g. the high molecular weight proteins and the τ factor, contain several polypeptides. A distinct group of these associated proteins possesses an isoelectric point of 9.5, and molecular weights between 72000 and 280000 daltons. This family of basic proteins is not the result of proteolytic cleavage of one high molecular weight precursor, as could be shown by fingerprint methods. A separation of native MAPS is briefly described.