Purification of a low molecular weight microtubule binding protein from sea urchin eggs.

A low molecular weight microtubule binding protein(SU-MAP34) was purified from sea urchin eggs. This protein bound strongly to the microtubule formed from purified echinoderm tubulin but showed no cross-linking of microtubules. Monospecific antibody against SU-MAP34 was produced and an immunoblotting analysis showed that this protein was not a breakdown product of a protein of a higher molecular mass. Whole cell staining and confocal laser scanning microscope observation showed that SU-MAP34 localized on the filamentous structure of mitotic apparatus and this structure was identified as the microtubule with double staining using anti-SU-MAP34 and anti-tubulin. An immunoblotting experiment showed an enrichment of SU-MAP34 in a microtubule protein fraction prepared using taxol from a crude extract of the cell.