Investigations of Sso7d catalytic residues by NMR titration shifts and electrostatic calculations.

Sso7d is a small basic protein consisting of 62 amino acids isolated from the thermoacidophilic archeobacterium Sulfolobus solfataricus. The protein is endowed with DNA binding properties, RNase activity, and the capability of rescuing aggregated proteins in the presence of ATP. In this study, the electrostatic properties of Sso7d are investigated by using the Poisson-Boltzmann calculation of the surface potential distribution and following by NMR spectroscopy the proton chemical shift pH titration of acidic residues.