A novel 24-kDa microtubule-associated protein purified from sea urchin eggs

Analysis of cytoskeletal and motility proteins in the sea urchin genome assembly

The sea urchin embryo is a classical model system for studying the role of the cytoskeleton in such events as fertilization, mitosis, cleavage, cell migration and gastrulation. We have conducted an analysis of gene models derived from the Strongylocentrotus purpuratus genome assembly and have gathered strong evidence for the existence of multiple gene families encoding cytoskeletal proteins and their regulators in sea urchin. While many cytoskeletal genes have been cloned from sea urchin with sequences already existing in public databases, genome analysis reveals a significantly higher degree of diversity within certain gene families. Furthermore, genes are described corresponding to homologs of cytoskeletal proteins not previously documented in sea urchins. To illustrate the varying degree of sequence diversity that exists within cytoskeletal gene families, we conducted an analysis of genes encoding actins, specific actin-binding proteins, myosins, tubulins, kinesins, dyneins, specific microtubule-associated proteins, and intermediate filaments. We conducted ontological analysis of select genes to better understand the relatedness of urchin cytoskeletal genes to those of other deuterostomes. We analyzed developmental expression (EST) data to confirm the existence of select gene models and to understand their differential expression during various stages of early development.

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.