Characterisation of a mutant from Escherichia coli lacking protein L15 and localisation of protein L15 by immuno-electron microscopy.

Two mutants lacking protein L15 from the ribosome as determined by two dimensional gels were investigated using a number of different immunological methods. One strain was found to possess several protein L15 moieties which differed in net charge and in size. The other showed no evidence of L15 cross-reacting material (CRM) on the ribosome or in the supernatant. Ribosomes of this strain were used as a control in the process of the localisation of protein L15 on the surface of the large subunit of Escherichia coli ribosomes. Antigenic determinants mapped in the angle between the central protuberance and the L1 protuberance. Protein L15 has been assigned a central role in the large subunit in vitro assembly map, in peptidyltransferase activity and in the binding of erythromycin, so the significance of a mutant lacking this protein is discussed.