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Hemin and bile pigments are the secondary structure regulators of intrinsically disordered antimicrobial peptides

Zsila, Ferenc and Juhász, Tünde and Bősze, Szilvia and Horváti, Kata and Beke-Somfai, Tamás (2018) Hemin and bile pigments are the secondary structure regulators of intrinsically disordered antimicrobial peptides. CHIRALITY: THE PHARMACOLOGICAL BIOLOGICAL AND CHEMICAL CONSEQUENCES OF MOLECULAR ASYMMETRY, 30 (2). pp. 195-205. ISSN 0899-0042

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Abstract

The interaction of protoporphyrin compounds of human origin with the major bee venom component melittin (26 a.a., Z +6) and its hybrid derivative (CM15, 15 a.a., Z +6) were studied by a combination of various spectroscopic methods. Throughout a two-state, concentration-dependent process, hemin and its metabolites (biliverdin, bilirubin, bilirubin ditaurate) increase the parallel β-sheet content of the natively unfolded melittin, suggesting the oligomerization of the peptide chains. In contrast, α-helix promoting effect was observed with the also disordered but more cationic CM15. According to fluorescence quenching experiments, the sole Trp residue of melittin is the key player during the binding, in the vicinity of which the first pigment molecule is accommodated presumably making indole-porphyrin π-π stacking interaction. As circular dichroism titration data suggest, cooperative association of additional ligands subsequently occurs, resulting in multimeric complexes with an apparent dissociation constant ranged from 20 to 65 μM. Spectroscopic measurements conducted with the bilirubin catabolite urobilin and stercobilin refer to the requirement of intact dipyrrinone moieties for inducing secondary structure transformations. The binding topography of porphyrin rings on a model parallel β-sheet motif was evaluated by absorption spectroscopy and computational modeling showing a slipped-cofacial binding mode responsible for the red shift and hypochromism of the Soret band. Our results may aid to recognize porphyrin-responsive binding motifs of biologically relevant, intrinsically disordered peptides and proteins, where transient conformations play a vital role in their functions.

Item Type: Article
Uncontrolled Keywords: Melittin; INTRINSIC DISORDER; Hemin; fluorescence quenching; CM15; circular dichroism spectroscopy; Biliverdin; bilirubin; SPECTROSCOPY; CONFORMATION; PROTEINS; BINDING; bee venom; BETA-LACTOGLOBULIN; MONOMERIC MELITTIN; AQUEOUS-SOLUTION; INDUCED CIRCULAR-DICHROISM
Subjects: Q Science / természettudomány > QD Chemistry / kémia
SWORD Depositor: MTMT SWORD
Depositing User: MTMT SWORD
Date Deposited: 05 Feb 2018 14:33
Last Modified: 01 Dec 2018 00:15
URI: http://real.mtak.hu/id/eprint/73894

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