RESUMEN
1H nuclear magnetic resonance experiments have shown that the amide hydrogens of residues 30 to 40 of bacteriophage Pf1 coat protein in micelles undergo very slow exchange with solvent deuterons. The amide 1H resonances from these residues were used to monitor the structural stability of the membrane-spanning helix of the coat protein during the transition of the coat protein from its structural form, in the virus particle, to the membrane-bound form, in micelles. The helix was found to remain folded on the 10(-3) second time-scale of the experiment, which indicates that no major disruption or rearrangement of the central part of the protein structure occurs during the process of coat protein solubilization by detergent. The results also suggest that a helical peptide can associate with lipids without reorganization of its secondary structure. However, a general model for the insertion of proteins into membranes cannot be established from these results, because the mechanism of the detergent solubilization process may differ somewhat from that of the membrane insertion process.
Asunto(s)
Cápside , Colifagos/análisis , Colifagos/efectos de los fármacos , Espectroscopía de Resonancia Magnética , Micelas , Conformación Proteica , Dodecil Sulfato de Sodio/farmacologíaRESUMEN
The major coat protein of filamentous bacteriophage adopts its membrane-bound conformation in detergent micelles. High-resolution 1H and 15N NMR experiments are used to characterize the structure and dynamics of residues 30-40 in the hydrophobic midsection of Pf1 coat protein in sodium dodecyl sulfate micelles. Uniform and specific-site 15N labels enable the immobile backbone sites to be identified by their 1H/15N heteronuclear nuclear Overhauser effect and allow the assignment of 1H and 15N resonances. About one-third of the amide N-H protons in the protein undergo very slow exchange with solvent deuterons, which is indicative of sites in highly structured environments. The combination of results from 1H/15N heteronuclear correlation, 1H homonuclear correlation, and 1H homonuclear Overhauser effect experiments assigns the resonances to specific residues and demonstrates that residues 30-40 of the coat protein have a helical secondary structure.