MAPPING THE STRUCTURE OF A NONNATIVE STATE OF STAPHYLOCOCCAL NUCLEASE

Non-native states of proteins populated at extremes of pH, or by mutat ion or truncation of the protein sequence, are thought to be equilibri um models for kinetic intermediates on the folding pathway. While the global physical properties of these molecules have been well character ized, analysis of their structure by NMR spectroscopy has proven diffi cult. Here we report the use of a new chemical cleavage technique, bas ed on reactive oxygen species, to map the backbone fold of a truncated form of staphylococcal nuclease in a non-native state. The fragment a dopts a native-like fold, however the technique also reveals regions o f nonnative structure.