Sedimentation Studies on the Interaction of Ribosomal Subunits from Escherichia coli (II)

The First Department of Physiology (Supervised by Prof. Yutaka Tashiro), Kansai Medical School We have previously shown that 60S component and the dimer of D-30S ribosomal subunits may exist in the course of dissociation from and association to 70S ribosomes of E. coli. To obtain more direct evidences for the possibilities, we have examined the intPrartinn between islated ribosomal subunits by sucrose density gradient centrifugation and obtained the following results: (a) Among D-50S, D-30S, N-50S and N-30S ribosomal subunits, D-30S ribosomal subunits only can combine together to form the dimer with the sedimentation coefficient of 50S, (b) N-50S ribosomal subunits can't combine with both N-30S and D-30S ribosomal subunits, (c) N-30S ribosomal subunits can combine with derived 50S ribosomal subunits to form various forms of particles corresponding to about 40S,45S,50S,60S,64S and 72S, (d) D-50S and D-30S ribosomal subunits can combine together to form 70S ribosomes but their combining ability decreases by purification and (e) 60S component seems to be swollen 70S ribosomes weakly bound. The combining character of ribosomal subunits has been discussed.