title: Crystal structure of neocarzinostatin, an antitumor protein-chromophore complex.
abstract: Structures of the protein-chromophore complex and the apoprotein form of neocarzinostatin were determined at 1.8 angstrom resolution. Neocarzinostatin is composed of a labile chromophore with DNA-cleaving activity and a stabilizing protein. The chromophore displays marked nonlinearity of the triple bonds and is bound noncovalently in a pocket formed by the two protein domains. The chromophore pi-face interacts with the phenyl ring edges of Phe52 and Phe78. The amino sugar and carbonate groups of the chromophore are solvent exposed, whereas the epoxide, acetylene groups, and carbon C-12, the site of nucleophilic thiol addition during chromophore activation, are unexposed. The position of the amino group of the chromophore carbohydrate relative to C-12 supports the idea that the amino group plays a role in thiol activation.
authors.affiliation: Division of Chemistry and Chemical Engineering, California Institute of Technology, Pasadena 91125.
authors.forename: K H
authors.initials: KH
authors.lastname: Kim
authors.forename: B M
authors.initials: BM
authors.lastname: Kwon
authors.forename: A G
authors.initials: AG
authors.lastname: Myers
authors.forename: D C
authors.initials: DC
authors.lastname: Rees
mesh_terms: D001059:Apoproteins / Q000737:chemistry; D003196:Computer Graphics; D003198:Computer Simulation; D018360:Crystallography, X-Ray; D006860:Hydrogen Bonding; D008958:Models, Molecular; D011487:Protein Conformation; D017433:Protein Structure, Secondary; D009353:Zinostatin / Q000737:chemistry*
chemical_list: D001059:Apoproteins; D009353:Zinostatin