The properties of ribosomal proteins from a moderate halophile

The ribosomes from the extreme halophile Halobacterium cutirubrum are unusual in that their ribosomal proteins are acidic rather than basic as is the case with almost all bacterial ribosomes (Bayley, S.T. (1966) J. Mol. Biol. 15, 420-427). To determine whether the ribosomes of a moderate halophile show similar properties the ribosomal proteins from an unidentified moderate halophile, which grows over a wide range of NaCl concentrations (0.04-4.3 M), were compared to those of Escherichia coli and H. cutirubrum. The proteins are slightly more acidic than those of E. coli but much less acidic than those from the extreme halophile as judged by their mobility on polyacrylamide gels and their amino acid composition. The electrophoretic profile on polyacrylamide gels of the ribosomal proteins from the moderate halophile is similar whether the cells are grown in 0.5 M or 4.25 M NaCl.