Eukaryotic tryptophanyl-tRNA synthetase acquires affinity to high molecular weight RNA after limited proteolysis

It is shown that the native tryptophanyl-tRNA synthetase (Mr 2X60 kDa) isolated from bovine pancreas does not interact with high-molecular weight RNAs (E. coli rRNAs). The enzyme acquires the affinity for high-molecular weight RNAs after the cleavage of the 20 kDa fragment from each of the subunits upon digestion by protease. The possible functional significance of the discovered phenomenon is discussed.     

The channel function of the hydrophobic fragment of Ca ATPase in the sarcoplasmic reticulum of rabbit skeletal muscles in the early period after x-ray radiation exposure

At early times (1 and 24 h) following local single exposure of rabbit hindlimbs to 0.21 C/kg X-radiation Ca ATPase was isolated from sarcoplasmic reticulum of skeletal muscles and inserted in liposomes the treatment of which with trypsin resulted in the formation of proteoliposomes with a Ca ATPase hydrophobic fragment (Mr 45-50 kDa). It was shown that X-radiation increased the permeability of univalent and bivalent cations through a channel formed by the hydrophobic fragment of Ca ATPase and diminished ion selectivity of this channel.