Extraction and some properties of the proteins, Spastin B, from the spasmoneme of Carchesium polypinum.

Proteins of the contractile spasmoneme from Carchesium polypinum were extracted in 2% SDS, 30% acetic acid, or 8 M urea. The proteins extracted in SDS had a wide molecular weight distribution when examined by SDS-polyacrylamide gel electrophoresis. On the other hand, the proteins extracted in urea and acetic acid had three major peaks with molecular weights of about 16,000, 18,000, and 22,000. Most of these proteins were soluble even in the absence of urea and furthermore were found to be monomeric, since the sedimentation coefficient, s20,w, measured by analytical ultracentrifugation was 2.0S. The electrophoretic mobility of the proteins extracted in urea or in acetic acid was examined on alkaline gels. In the presence of free Ca2+, the mobility was significantly reduced compared with that in the absence of free Ca2+. These Ca-binding proteins were heat-stable and could not interact with troponin I. The implications of these proteins and others in relation to the contractility of the spasmoneme in Carchesium stalk are discussed.