Factors governing electron capture by small disulfide loops in two-cysteine peptides.
Integrated molecular orbital-molecular orbital (IMOMO) calculations on 17 short disulfide-bridged peptides (up to 16 residues, with at most five intraloop residues) were performed to elucidate some factors controlling their electron capture. These illustrative systems display contrasted behaviors, shedding light on several criteria of differentiation: size, shape, and rigidity of the disulfide-linking loop, intramolecular hydrogen bonds, etc. The geometrical malleability of disulfide radical anions, whose existence and role as intermediate have been evidenced, is discussed. The disulfide elongation (by ca. 0.7 A) upon electron capture induces "soft" structural damages for these turn structures, with a weakening or cleavage of vicinal hydrogen bond(s). On the basis of a series of six Cys-Alan-Cys peptides, it is proposed that electron affinity reflects the topological frustration of these short and highly constrained structures. Results for a series of amino acid mutations are analyzed for the Cys-Xxx-Yyy-Cys motif, common to redox enzymes of the thioredoxin superfamily.
Equipe de Chimie et Biochimie Théoriques, UMR 7565 CNRS-UHP, Institut Jean Barriol, (FR CNRS 2843), Faculté des Sciences et Techniques, Nancy-Université, B.P. 239, 54506 Vandoeuvre-lès-Nancy, France. Elise.Dumont@cbt.uhp-nancy.fr
Elise
E
Dumont
Pierre-François
PF
Loos
Xavier
X
Assfeld
D003545:Cysteine / Q000737:chemistry*; D004220:Disulfides / Q000737:chemistry*; D004583:Electrons; D006860:Hydrogen Bonding; D008958:Models, Molecular; D010088:Oxidoreductases / Q000737:chemistry; D010455:Peptides / Q000737:chemistry*; D011487:Protein Conformation; D013879:Thioredoxins / Q000737:chemistry
D004220:Disulfides; D010455:Peptides; D013879:Thioredoxins; D010088:Oxidoreductases; D003545:Cysteine