Enrichment of Legumin mRNA by Immunoadsorption of Membrane-bound Polysomes from Developing Field Bean Seeds (Vicia faba L. var. minor)

Abstract

Summary Polysomes synthesizing legumin were isolated by immunoadsorption using anti-legumin IgG from rabbits and anti-rabbit IgG-PAB-cellulose. The poly(A)-containing RNA from immunoselected membrane-bound polysomes exhibits a M r of 0.76 × 10 6 similar to the M r of the predominant peak of poly(A)-containing RNA from total mb polysomes which in addition shows minor components of M r 0.82–0.83 × 10 6 and 0.53 × 10 6 on a sucrose density gradient. Two legumin precursor polypeptides of Mr 64,000 and 67,000 were obtained by cell-free translation of poly(A)-containing RNA from immunoselected mb polysomes in the wheat germ system. Densitometer traces of in vitro translation products directed by poly(A)-containing RNA from both total mb polysomes and the immunoselected mb polysomes led to the calculation of an enrichment of 60–70% for the legumin mRNA by immunoselection of polysomes. No higher degree of enrichment could be achieved since polysomal aggregation and unspecific adsorption of the storage globulins to the polysomes interfere with the immunoselection procedure.