Lack of coupling between secondary structure formation and collapse in a model polypeptide that mimics early folding intermediates, the F2 fragment of the Escherichia coli tryptophan-synthase beta chain.

摘要: The isolated, 101-residue long C-terminal (so called F2) fragment of the beta chain from Escherichia coli tryptophan synthase was shown previously to fold into an ensemble conformations that are condensed, contain large amounts highly dynamic secondary structures, and behave as a good model structured intermediates form at very early stages protein folding. Here, solvent perturbations were used investigate forces involved in stabilizing structure (monitored by far-UV CD) condensation polypeptide light scattering) isolated F2. It observed neither ionic strength, nor pH (between 7 10), salts Hofmeister series affected global contents F2, whereas some these collapse slightly. Addition trifluoroethanol resulted increase both amount Stokes radius Conversely, F2 became more condensed upon raising temperature 4 60 degrees C, this range, undergoes significant melting. These observations lead conclusion that, there is no coupling between hydrophobic structure. This finding will be discussed terms events