Isolation and initial characterization of the mammalian midbody

Midbodies were isolated from synchronized cultures of Chinese hamster ovary (CHO) cells and their protein composition was studied by means of SDS PAGE. Gels of the midbodies included alpha and beta tubulins as major bands (approximately 30% of the total protein) and approximately 35 other bands, none of which constituted greater than 3.5% of the total protein. Extraction of the isolated midbodies with Sarkosyl NL-30- solubilized the midbody microtubules but left the central, dense matrix zone of the midbody intact. A protein doublet of approximately 115,000 mol wt was retained preferentially by the particulate fraction containing the matrix zones, indicating it to be a component of the matrix. The 115,000 mol wt doublet was also present in gels of isolated mitotic spindles from CHO cells. The overall protein composition of the isolated spindles was very similar to that of the isolated midbodies.