An investigation of the conformational properties of ribosomes using N-ethylmaleimide as a probe.

The reactivity of ribosomal proteins towards N-ethylmaleimide has been examined in a variety of ribosome and ribosomal subunit preparations from Escherichia coli. The data show that samples which would be regarded as equivalent operationally can differ significantly in conformation, as judged by reactivity, depending on the method of preparation. The washing of ribosomes with high concentrations of salt has a particularly dramatic effect on protein reactivity. The implications of these results for our understanding of ribosome conformation and for the further study of conformation by chemical reactivity are discussed.