The aromatic amino acid content of the bacterial chaperone protein groEL (cpn60) Evidence for the presence of a single tryptophan

Studies of the absorption and fluorescence properties of the chaperone protein groEL (cpn60) from Escherichia coli show that tryptophan is present, in contrast to the proposed amino acid sequence of the protein (Hemmingsen, S.M. et al. (1988) Nature 333, 330–334). By determining a suitable value for the specific absorption coefficient of the protein at 280 nm, it has been shown that the content of the aromatic amino acids corresponds to a single tryptophan and (most probably) seven tyrosines per subunit ( M r 57 200).