Outer dense fibre protein 2 (ODF2) is a major protein of sperm tail outer dense fibres which are prominent sperm tail-specific cytoskeletal structures. Moreover, ODF2 was also identified as a widespread component of the centrosomal scaffold and was found to associate preferentially with the appendages of the mother centriole [Nakagawa, Y., Yamane, Y., Okanoue, T., Tsukita, S. and Tsukita, S. (2001) Mol. Biol. Cell 12, 1687-1697]. Secondary structure predictions indicated ODF2 as an overall coiled-coil protein with a putative fibre forming capacity. To investigate its potential functions in generating the centrosomal scaffold and in microtubule nucleation we asked whether ODF2 is able to form a fibrillar structure by self-association in vivo and if it interacts with microtubules. By cytological investigation of transfected mammalian cells expressing ODF2-GFP fusion proteins and in vitro coprecipitation assays we could demonstrate that ODF2 is a self-interacting protein that forms a fibrillar structure partially linked to the microtubule network. Microtubule cosedimentation and coprecipitation assays indicated ODF2 as a microtubule-associated protein. However, we could not demonstrate a direct interaction of ODF2 with tubulin, suggesting that binding of endogenous ODF2 to the axonemal as well as to centrosomal microtubules may be mediated by, as yet, unknown proteins.

Abbildung 21 Vergleich der subzellulären Organisation der Odf1-NC-ECFP einzeltransfizierten mit Odf1-NC-CFP und Odf2-NC-YFP