tification of centrosome proteins. It has been shown that the centrosome of the loach spermatozoa consists of a
pair of centrioles of the standard structure and contains the marker protein
-tubulin, cytoplasmic microtubules branch out from it, and it does not contain any additional structures characteristic of the centrosomes of sper-
matozoa of many other fishes. A preparation enriched with intact centrosomes was obtained from the loach
spermatozoa. These centrosomes contained
-tubulin, although they had lost their ability to induce the polymer-ization of microtubules. The preparation of loach centrosomes was successfully used to obtain a set of mono-
clonal antibodies against the mammalian centrosome. A new protein kinase LOSTEK was identified with the
help of one of these monoclonal antibodies, SN2-3D2, which was localized in the centrosome and then on
microtubules in both loach spermatozoa and cultured mammalian cells. Hence, the loach spermatozoa are a
promising means to identify new proteins in the mammalian centrosome.