Preliminary crystallographic study of macromomycin

Crystal structure analysis of auromomycin apoprotein (macromomycin) shows importance of protein side chains to chromophore binding selectivity

The crystal structure of macromomycin, the apoprotein of the antitumor antibiotic auromomycin, has been determined and refined at 1.6-A resolution. The overall structure is composed of a flattened seven-stranded antiparallel beta-barrel and two antiparallel beta-sheet ribbons. The barrel and the ribbons define a deep cleft that is the chromophore binding site. The cleft is very accessible and in this structure is occupied by two 2-methyl-2,4-pentanediol and two water molecules. The overall shape of the binding site is similar to that of the analogue actinoxanthin. Highly specific side chains that are not conserved between different analogues extend into the binding site and may be important to the chromophore binding specificity.

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.

Structural study of crystalline auromomycin. Preliminary X-ray diffraction study of auromomycin and macromomycin

Auromomycin and macromomycin from the organism Streptomyces macromomyceticus have been crystallized. The X-ray diffraction pattern of crystals of each molecule is consistent with space group P2(1)2(1)2 with cell parameters a = 46.45 A, b = 54.34 A and c = 42.03 A for auromomycin, and a = 46.45 A, b = 54.52 A and c = 41.54 A for macromomycin. Diffraction analysis of auromomycin is in progress.