A protein involved in the peptidyltransferase activity of Escherichia coli ribosomes.

Cores were prepared from 50S ribosomal subunits by incubation with 0.4 M LiCl/Mg(++) (0.4c cores); 0.8c cores and corresponding SP(0.4-0.8) split proteins were obtained from 0.4c cores. In the fragment reaction 0.4c cores were active, but 0.8c cores were not. Activity of the 0.8c cores could be restored by reconstitution with the SP(0.4-0.8) fraction. The split proteins were separated by DEAE-cellulose chromatography and Sephadex gel filtration. The peptidyltransferase activity is correlated with the amount of protein L11 added to the 0.8c core under reconstitution conditions. Whether protein L11 displays the enzymatic activity itself or is part of the enzymatic center is discussed.