Conformational properties of the protease from Staphylococcus aureus studied by circular dichroism

The conformational properties of the protease from Staphylococcus aureus strain V8 were studied by the CD probe. The CD spectra in the far ultraviolet zone displayed a negative band at 205–207 nm but no positive bands were observed at 191–198 nm. This indicates that the protease was devoid of significant amounts of the α-helix and pleated sheet conformations, i.e., that the polypeptide chain was folded into a unique irregular (aperiodic) conformation. The structure was relatively insensitive to sodium dodecyl sulfate and high concentrations of aliphatic alcohols but it was readily perturbed by acid and alkali. This suggests that the three-dimensional structure of this protein is stabilized chiefly by electrostatic interactions. Significant differences in the tertiary structure of the protease were indicated by the CD spectra at the two enzyme activity maxima (pH 4.1 and pH 7.6–8.2).