Interaction of biotin and biotinyl derivatives with avidin: conformational changes upon binding

Autor: Giancarlo Fini, G. Bottura, Armida Torreggiani
Rok vydání: 2000
Předmět:
Zdroj: Journal of Raman Spectroscopy. 31:445-450
ISSN: 1097-4555
0377-0486
DOI: 10.1002/1097-4555(200005)31:5<445::aid-jrs556>3.0.co;2-g
Popis: We used FT-Raman and FT-IR spectroscopy to study avidin and its complexes with some biotin and biotinyl derivatives where the COOH group of the pentanoic acid chain is substituted by an ester or amidic group. To investigate the small structural changes due to the binding, the amide I Raman bands of Avidin and its complexes were analysed by two fairly comparable methods. The vibrational results indicate that the interaction with the ligands slightly modifies the secondary structure of the protein, decreasing the β-sheet content and increasing the α-helix percentage. To confirm the results obtained by Raman spectroscopy, we performed Gaussian curve-fitting procedure of the amide I and III infra-red regions of neat avidin and its complexes. The percentages obtained from the analysis of the Raman and IR spectra show the same trend. Thus, IR spectroscopy as an alternative or adjunct to Raman spectroscopy is a useful tool in evaluating small structural modifications produced by a bound ligand on a protein. The structural changes are mainly due to modifications in the hydrogen bonds with the pentanoic acid moiety of the ligand and, probably, are ascribed to conformational modifications in the surface loop which binds the strands of the β-barrel. In fact, biotin-N-succinimidyl ester, as well as biotin hydrazide, which have the same ability in the hydrogen-bond formation compared with biotin, induces avidine conformational changes similar to those observed in the avidin–biotin complex. The terminal group of the biotin derivatives seems to have a slight influence since the structural modifications of the protein observed upon the binding of the long-chain hydrazide-derivative ligands (biotinyl-aminocaproic hydrazide and biocitin hydrazide) are slightly greater than those obtained with the corresponding COOH containing ligands (biotinyl-aminocaproic acid and biocytin). Although the hydrogen bonds formed by the pentanoic acid chain of biotin are not essential to complex formation since they are not directly involved in the active site, the present study confirms that they can interact with the loops that lock biotin in the β-barrels of avidin and modulate the strength of the protein-ligand interaction. Copyright © 2000 John Wiley & Sons, Ltd.
Databáze: OpenAIRE
Externí odkaz: