Amino acid sequences fold into three-dimensional shapes of proteins that are the key players in all aspects of the life of cells. Recent publications of the human genome sequence and other genome projects have provided unprecedented amounts of sequences, which have stirred great hopes for understanding and curing diseases. In contrast to the vast amount of sequence data, corresponding protein structure and function data is scarce. Therefore the study of protein folding in general is of interest for a very broad audience. In this context, it is particularly intriguing why evolution has selected out of the pool of possible sequences those observed in actual genomes. One hypothesis is that those sequences capable of forming appropriate contacts at the beginning of folding have been selected. These contacts should allow an amino acid chain to fold into a functional three-dimensional shape and avoid contacts that result in misfolding. Our study focused on the characterization of the dynamics of an unfolded protein, lysozyme. The study has importance for understanding the molecular mechanism of folding but may also shed light on when the folding process goes wrong—such as in misfolding diseases, including Alzheimer's.

  Does it describe a new discovery or a new methodology that's useful to others?

We studied the dynamic properties of unfolded lysozyme by using NMR spectroscopy. While this type of analysis had proven useful for study of unfolded proteins before, the contribution this paper made was to identify long-range interactions at this initial stage of folding using a combination of NMR spectroscopy and site-directed mutagenesis. We showed that there are several clusters of residual structure in unfolded lysozyme and these are disrupted by a single point mutation of a tryptophan that is not in contact with all of the clusters in the native structure. This study therefore not only addresses the question of what role hydrophobic clusters in unfolded proteins play for the folding process, but it also demonstrated that these clusters are stabilized by long-range interactions.

  Could you summarize the significance of your paper in layman's terms?

The observation has fundamental significance for the understanding of protein folding by identification of long-range stabilizing interactions of hydrophobic clusters in protein conformations at the very early stages of protein folding, namely in unfolded proteins. The non-native character of some of these interactions suggest that these clusters may also be involved in misfolding, a phenomenon common to a number of important diseases.

  How did you become involved in this research?

During my Ph.D. thesis I worked on the study of conformational changes and misfolding of rhodopsin, a membrane protein. The research described in this publication was my main research project while being a postdoctoral researcher in the laboratory of Professor Harald Schwalbe. The study of protein folding at the atomic level using NMR spectroscopy is one of his major interests.

Judith Klein-Seetharaman
Assistant Professor
Department of Pharmacology
University of Pittsburgh School of Medicine
Pittsburgh, PA, USA

Harald Schwalbe
Professor
Institut für Organische Chemie
Johann Wolfgang Goethe-Universität
Frankfurt am Main , Germany