An NMR investigation of the conformational effect of nitroxide spin labels on Ala-rich helical peptides.
J Magn Reson
; 131(2): 248-53, 1998 Apr.
Article
em En
| MEDLINE
| ID: mdl-9571100
ABSTRACT
Nitroxide spin labels, in conjunction with electron spin resonance (ESR) experiments, are extensively employed to probe the structure and dynamics of biomolecules. One of the most ubiquitous spin labeling reagents is the methanethiosulfonate spin label which attaches a spin label selectively to Cys residues via a disulfide bond (Cys-SL). However, the actual effect of the nitroxide spin label upon the conformation of the peptide or protein cannot be unambiguously determined by ESR. In this study, a series of 16-residue Ala-rich helical peptides was characterized by nuclear magnetic resonance techniques. The C alpha H chemical shift analysis, NOEs, and 3JNH alpha coupling constants for peptides with no Cys, free Cys, and Cys-SL (with the N-O group reduced) were compared. These results indicate that while replacement of an Ala with a Cys residue causes a loss of overall helical structure, the Cys-SL residue is helix supporting, as would be expected for a non-beta-branched aliphatic amino acid. Thus, the Cys-SL residue does not perturb helical structure and, instead, exhibits helix-stabilizing characteristics similar to that found for Ala, Met, and Leu.
Buscar no Google
Base de dados:
MEDLINE
Assunto principal:
Peptídeos
/
Marcadores de Spin
/
Espectroscopia de Ressonância Magnética
/
Estrutura Secundária de Proteína
/
Mesilatos
/
Óxidos N-Cíclicos
/
Alanina
Idioma:
En
Revista:
J Magn Reson
Assunto da revista:
DIAGNOSTICO POR IMAGEM
Ano de publicação:
1998
Tipo de documento:
Article
País de afiliação:
Estados Unidos