Protein labelling patterns in oocytes of Xenopus laevis

Soluble and microsomal proteins synthesized at various stages of oogenesis in Xenopus laevis were compared by 3H and 14C dual-isotope labelling with subsequent mixing and analysis on sodium dodecyl sulfate (SDS)-polyacrylamide gels. The results indicated that the proteins labelled in all the stages of oogenesis studied are remarkably similar. However, the patterns in the small and medium-sized oocytes are more similar to one another than to the patterns characteristic of large oocytes. The greatest differences were found when comparing the microsomal proteins. The labelling patterns of oocyte proteins in vitro were not significantly different from the in vivo patterns for the stages of oogenesis studied. These results indicate that (1) there is little quantitative contribution of proteins to either the soluble or microsomal fractions from extra-oocytic sources in vivo and (2) the in vitro system itself has little effect on the labelling patterns over the incubation period.