An Experimental Approach to the Study of the Folding of Staphylococcal Nuclease

Abstract

Two inactive fragments of staphylococcal nuclease (a protein consisting of 149 residues, devoid of sulfhydryl groups and disulfide bonds) have been prepared; one (nuclease-P(,126)) contains Residues 1 through 126, and the other (nuclease-P(127_ 49)) contains Residues 127 through 149. Studies of nuclease-P(I 1 26), employing circular dichroism, optical rotation, immunodiffusion, and solvent perturbation, reveal a loose and disorganized structure very different from that of nuclease. Nuclease-P( 127 .149) is also structureless, as determined by measurements of circular dichroism and the fluorescence spectrum of the tryptophan residue.