Development of microbody membrane proteins during the transformation of glyoxysomes to leaf peroxisomes in pumpkin [Cucurbita sp.] cotyledones
1995
Yamaguchi, K. (National Inst. for Basic Biology, Okazaki, Aichi (Japan)) | Takeuchi, Y. | Mori, H. | Nishimura, M.
The microbody transition observed in the cotyledons of some fatty seedlings involves the conversion of glyoxysomes to leaf peroxisomes. To clarify the molecular mechanisms underlying the microbody transition, we established a method for the preparation of highly purified microbodies. SDS-PAGE and immunoblot analysis of isolated microbodies from pumpkin cotyledons at various stages showed that glyoxysomal enzymes are replaced by leaf-peroxisomal enzymes during the microbody transition. Two proteins in glyoxysomal membranes, with molecular masses of 31 kDa and 28 kDa, were not solubilized from the membranes with 0.2 M KCl, an indication that these proteins are bound tightly with glyoxysomal membranes. Their polyclonal antibodies were raised against the respective purified protein. Immunoblot analysis of subcellular fractions and immunogold analysis confirmed that these proteins were specifically localized on glyoxysomal membranes. Analysis of these membrane proteins during development revealed that the amounts of these membrane proteins decreased during the microbody transition and that the large one was retained in leaf peroxisomes, whereas the small one could not be found in leaf peroxisomes after completion of the microbody transition. The results clearly showed that membrane proteins in glyoxysomes change dramatically during the microbody transition, as do the enzymes in the matrix
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