title: Conformations of protein moieties and chromophore-protein interactions in the antitumor antibiotics, macromomycin and auromomycin, characterized by IR and CD spectral analysis.
abstract: The free chromophores (chr) extracted from macromomycin (MCR) and auromomycin (AUR) showed different IR spectra in KBr tablets and different CD spectra in ethanol or methanol solution. Chr-MCR contained a greater amount of alkyl moieties than chr-AUR as shown by much stronger IR absorbance at 2960 cm-1. The IR spectra of MCR, AUR and their apo-proteins (apo) in D2O showed that major parts of the proteins formed antiparallel beta-pleated sheets. Apo-AUR exhibited a faster H-D exchange than AUR, indicating existence of more extensive "nonmotile parts" of the beta-sheet formed through the chromophore-protein interaction in AUR. However, apo-MCR exhibited a slightly faster H-D exchange than MCR. This difference presumably was associated with the lower content of the chromophore (1.4 wt%) in MCR than that in AUR (8.2 wt%). Chr-AUR was extracted from the intact antibiotic with methanol more efficiently than chr-MCR. Further, a marked bathochromic effect by the chromophore-protein interaction was observed in the CD and UV absorption for MCR, but not for AUR. These results indicated that chr-MCR was tightly bound to the protein moiety while most of chr-AUR was loosely bound.
mesh_terms: D000900:Anti-Bacterial Agents; D000903:Antibiotics, Antineoplastic / Q000032:analysis*; D001059:Apoproteins / Q000032:analysis*; D002942:Circular Dichroism; D010455:Peptides / Q000032:analysis; D011487:Protein Conformation; D013055:Spectrophotometry, Infrared; D013056:Spectrophotometry, Ultraviolet
chemical_list: D000900:Anti-Bacterial Agents; D000903:Antibiotics, Antineoplastic; D001059:Apoproteins; D010455:Peptides; C001666:auromomycin