Crystallographic studies of protein denaturation and renaturation. 2. Sodium dodecyl sulfate induced structural changes in triclinic lysozyme

Cross-linked triclinic lysozyme was denatured with sodium dodecyl sulfate. Removal of the denaturant resulted in a refolding of the protein to a conformation similar to but not identical with the native one. Three-dimensional x-ray diffraction data out to 3.2-A resolution were collected for two states in the refolding pathway, and appropriately weighted electron density difference maps were constructed. An analysis of these maps reveals that a sodium dodecyl sulfate molecule is trapped in the interior of the protein, and results in a separation of regions of the polypeptide chain. Our results are discussed in terms of current models for protein folding.