Turbidimetric and potentiometric studies of ribosomal subunits from an erythromycin resistant mutant of Escherichia coli.

Turbidimetric and potentiometric techniques were applied to the analysis of an EryR mutant. Results show that in the mutant, the 30S subunits are drastically altered, as indicated by a higher Mg2+ requirement for subunit association and by an important difference in the titratable groups. Replacement of parental 50S by mutant 50S subunits does not decrease the association capacity with 30S parental subunits, but a structural difference is detected in the mutant 50S with potentiometric measurements. The mutation results in decreased ribosomal in vitro activities at 22 degrees C including lowered polyphenylalanine synthesis, drastic altered initiation step and the loss of erythromycin binding to the ribosomes. The results extend previous observation of a gene eryC part in the maturation of both subunits.