Neocarzinostatin: interaction between the antitumor-active chromophore and the carrier protein.

Conformational analysis of neocarzinostatin, an antibiotic protein with antitumor activity, in its holo-state in solution was carried out by NMR-spectroscopy. The results showed a beta-barrel structure for the carrier protein, in which the chromophore is tightly enwrapped and thus shielded from exposure to the solvent. The three-dimensional structure of this complex led to the proposal of a possible mechanism for the exposure or release of the active principle due to subtle environmental changes, e.g., in pH.