Physical characteristics of the reconstitution intermediate RI50(1) from the 50 S ribosomal subunit of Escherichia coli.

The procedure for the in vitro reconstitution of active 50 S ribosomal subunits from Escherichiu coli first appeared in 1974 [ 11. The same group later reported the kinetic study of the reconstitution steps and gave the estimated sedimentation values of the reconstitution intermediates in sucrose gradient in 1976 [2]. Due to the relative difficulty in isolating the intermediates, no physical studies of these intermediates have yet been reported. We have isolated the first intermediate RI,,(,), which is homogeneous and stable under low salt conditions. We report here the physical characteristics of the RI,o(l) particle as determined by hydrodynamic methods and compare our results with the intact 50 S subunits, which have been characterized under the same buffer conditions.