A CHANGE IN THE PHOSPHORYLATION PATTERN OF THE 30000-33000 M(R) SYNAPTONEMAL COMPLEX PROTEINS OF THE RAT BETWEEN EARLY AND MID-PACHYTENE

The lateral elements (LEs) of synaptonemal complexes (SCs) of the rat contain major components with relative electrophoretic mobilities (M(r )s) of 30000-33000, which are the products of a single gene. After one -dimensional separation of SC proteins on polyacrylamide-SDS gels, the se components show up as two major bands, whereas upon two-dimensional electrophoresis they are resolved in at least 24 spots, which focus a t pH 6.5 to 9.5. In this paper we show that these spots represent phos phorylation variants. For the analysis of the phosphorylation of the 3 0000- to 33000-M(r) SC components during progression through meiotic p rophase we developed a procedure for isolation of fractions of testicu lar cells of the rat that are enriched in separate stages of meiotic p rophase. Analysis of the 30000- to 33000-M(r) SC components in these f ractions by two-dimensional electrophoresis and immunoblotting showed that phosphorylated variants of the 30000- to 33000-M(r) SC proteins o ccur throughout meiotic prophase. However, the extent of phosphorylati on changes between early and mid-pachytene, when one phosphate group i s probably added to each of the variants.