Isolation and characteristics of mRNPs associated with bound polyribosomes from the ewe lactating mammary gland

Abstract

The dissociation of bound polyribosomes from ewe lactating mammary gland, by EDTA or Puromycin-KC1 treatment releases Messenger Ribonucleoprotein particles (mRNP'S) which sediment in sucrose gradients as a single component having a sedimentation coefficient of about 22S. RNAs derived from mRNPs sediment between 9S and 15S and direct the synthesis of milk proteins in reticulocyte cell free systems. The mRNP protein moiety contains two major polypeptides with molecular weights of 52,000 and 72,000 daltons and two minor polypeptides with apparent molecular weights of 58,000 and 60,000 daltons.