Preliminary X-ray diffraction studies and biochemical characterization of the antitumor protein mitomalcin indicate close similarity to neocarzinostatin

The antitumor antibiotic protein mitomalcin, from the microorganism Streptomyces malayensis, has been purified to apparent homogeneity and crystallized. The crystals belong to space group P2(1)2(1)2(1) and have the following cell parameters: a = 27.2 A, b = 34.1 A, c = 101.7 A, and alpha = beta = gamma = 90 degrees. These crystal properties are extremely similar to crystals of the antitumor protein neocarzinostatin (11.7 kilodaltons kDa]) from Streptomyces carzinostaticus in spite of differing pH conditions for crystallizing the two proteins and an apparent difference in molecular weight. Gel electrophoresis shows the molecular weight is similar to that of neocarzinostatin. An amino acid composition analysis of mitomalcin indicates that some differences may exist between the two molecules, but a preliminary amino acid sequence analysis of the first 37 residues found no difference in the N-terminal region of the molecule.