Strategy for obtaining non-native protein cross-reactions

Most single-domain proteins show cooperative unfolding transitions at equilibrium: the cooperativity of protein folding makes it difficult to populate non-native protein structures [1,2]. Nevertheless, protein folding intermediates are known to exist [1,2] and alternative protein conformations have been demonstrated by numerous methods [2-41. A long-standing problem is how to populate non-native protein conformations (including protein folding intermediates) at high levels, so that their structures can be studied. This information is necessary to understand the mechanisms by which proteins fold, and to elucidate how signal transduction through proteins occurs. This paper considers trapping of non-native protein conformations using antibody cross-reactions, and describes an approach for characterizing the trapped species.