Amino acid functional groups involved in the binding of Escherichia coli ribosomal protein S1 to ribosomes and nucleic acids.

Histidine, arginine, tyrosine, lysine and cysteine residues of protein S1 were modified with diethyl pyrocarbonate & rose bengal, 2,3-butanedione (diacetyl), tetranitromethane, pyridoxal 5-phosphate, and N-ethyl-maleimide, respectively. Modification of the residues and the number of modified residues were determined by either fluorescence or UV spectroscopy. The effect of chemical modification on the function of protein S1 was studied with respect to nucleic acid (poly U and M13 ssDNA) binding and ribosome binding properties of the protein. We tested S1 binding to these two types of polynucleotides because of their reported (Draper et al. (1977) PNAS 74, 4786-4790) binding to two different sites on S1. The results indicate that histidine and lysine residues of S1 play an important role in the binding of S1 to both types of nucleic acids and that histidine and to some extent tyrosine residues are involved in the binding of S1 to ribosomes. The Data indicate the need for a re-evaluation of the two nucleic acid binding-site model.