title: Truncated staphylococcal nuclease is compact but disordered.
abstract: Deletion of 13 amino acids from the carboxyl terminus of the 149-amino acid staphylococcal nuclease molecule results in a denatured, partly unfolded molecule that lacks persistent secondary structure but is compact under physiological conditions. Since the modification is a carboxyl-terminal deletion, it is argued that the state resembles a peptide emerging from the ribosome just before the complete folding pathway is initiated. In this paper, we characterize the molecule by nuclear magnetic resonance, circular dichroism, and small-angle x-ray scattering measurements. The truncated nuclease shows wild-type levels of activity in the presence of calcium and is found to fold into a native-like conformation in the presence of 3',5'-bisphospho-2'-deoxythymidine, a potent inhibitor. Thus, the truncated molecule retains the capacity to fold. Our results suggest that extensive solvent exclusion generates a compact polypeptide chain prior to the development of persistent secondary structural features as a protein folds during biosynthesis.
authors.affiliation: Department of Molecular Biophysics and Biochemistry, Yale University, New Haven, CT 06511.
authors.forename: J M
authors.initials: JM
authors.lastname: Flanagan
authors.forename: M
authors.initials: M
authors.lastname: Kataoka
authors.forename: D
authors.initials: D
authors.lastname: Shortle
authors.forename: D M
authors.initials: DM
authors.lastname: Engelman
mesh_terms: D002942:Circular Dichroism; D009682:Magnetic Resonance Spectroscopy; D008836:Micrococcal Nuclease / Q000737:chemistry*; D011487:Protein Conformation; D011489:Protein Denaturation; D011994:Recombinant Proteins; D012542:Scattering, Radiation; D013210:Staphylococcus / Q000201:enzymology; D013329:Structure-Activity Relationship; D014867:Water; D014965:X-Rays
chemical_list: D011994:Recombinant Proteins; D014867:Water; D008836:Micrococcal Nuclease