Conformation studies on and assessment by spectral analysis of the protein-chromophore interaction of the macromolecular antitumor antibiotic C-1027.
Characterization of the secondary structure of the antitumor antibiotic C-1027 has been made from a comparison of C-1027 and its apoprotein by various analytical means. The results indicated the antibiotic to be abundant in beta-structure by measurements of Fourier-transform infrared (FT-IR) spectroscopy and the circular dichroism (CD) spectrum, and by a prediction of the secondary structure based on the amino acid sequence of the peptide. In comparison of the IR spectra of their proteins in D2O, the apoprotein exhibited a faster H-D exchange than C-1027, indicating an increase in the "non-motile parts" of the beta-sheets formed through the protein-chromophore interaction in holo-C-1027. The prediction of hydropathic index indicated the hydrophobic residues of the apoprotein to be predominantly located in the beta-sheet structures, suggesting hydrophobic interaction in the binding between chromophore and apoprotein. Further, the interaction between chromophore and apoprotein was detected by a fluorescence method. The result showed the dissociation constant (Kd) to be 6.88 x 10(-5) M, indicating that the chromophore is tightly bound to the protein moiety.
Otani
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Anticancer & Antimicrobial Research Laboratory, Taiho Pharmaceutical Co. Ltd., Tokushima, Japan.
D000595:Amino Acid Sequence; D000617:Aminoglycosides; D000900:Anti-Bacterial Agents; D000903:Antibiotics, Antineoplastic / Q000737:chemistry*; D001059:Apoproteins / Q000737:chemistry; D053281:Enediynes; D008968:Molecular Conformation; D008969:Molecular Sequence Data; D011506:Proteins / Q000737:chemistry; D013057:Spectrum Analysis
D000617:Aminoglycosides; D000900:Anti-Bacterial Agents; D000903:Antibiotics, Antineoplastic; D001059:Apoproteins; D053281:Enediynes; D011506:Proteins; C058024:C 1027