Key interactions in the immunoglobulin-like structure of apo-neocarzinostatin:: Evidence from nuclear magnetic resonance relaxation data and molecular dynamics simulations

The three-dimensional structure of apo-neocarzinostatin (apo-NCS. MW: ca. 11000. antitumoral chromophore carrier protein) is based on a seven-stranded antiparallel beta -sandwich, very similar to the immunoglobulin folding domain. We investigated the backbone dynamics of apo-NCS by C-13-NMR relaxation measurements and molecular dynamics simulation. Model-free parameters determined from the experimental data are compared with a 1.5-nsec molecular simulation of apo-NCS in aqueous solution. This comparison provides an accurate description of both local and collective movements within the protein. This analysis enabled us to correlate dynamic processes with key interactions of this beta -protein. Local motions that could be relevant for the intermolecular association with the ligand are also described.