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

The three-dimensional structure of apo-neocarzinostatin (apo-NCS. MW: ca. 1 1000. antitumoral chromophore carrier protein) is based on a seven-stranded antiparallel beta -sandwich, very similar to the immunoglobulin folding do main. We investigated the backbone dynamics of apo-NCS by C-13-NMR relaxati on measurements and molecular dynamics simulation. Model-free parameters de termined from the experimental data are compared with a 1.5-nsec molecular simulation of apo-NCS in aqueous solution. This comparison provides an accu rate description of both local and collective movements within the protein. This analysis enabled us to correlate dynamic processes with key interacti ons of this beta -protein. Local motions that could be relevant for the int ermolecular association with the ligand are also described.