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  • Title: Conformations of protein moieties and chromophore-protein interactions in the antitumor antibiotics, macromomycin and auromomycin, characterized by IR and CD spectral analysis.
    Author: Miwa N.
    Journal: J Antibiot (Tokyo); 1982 Nov; 35(11):1553-60. PubMed ID: 7161194.
    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.
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