Site-directed spin labeling and chemical crosslinking demonstrate that helix V is close to helices VII and VIII in the lactose permease of Escherichia coli.
AUTOR(ES)
Wu, J
RESUMO
Site-directed chemical cleavage of lactose permease indicates that helix V is in close proximity to helices VII and VIII. To test this conclusion further, permease containing a biotin-acceptor domain and paired Cys residues at positions 148 (helix V) and 228 (helix VII), 148 and 226 (helix VII), or 148 and 275 (helix VIII) was affinity purified and labeled with a sulfhydryl-specific nitroxide spin label. Spin-spin interactions are observed with the 148/228 and 148/275 pairs, indicating close proximity between appropriate faces of helix V and helices VII and VIII. Little or no interaction is evident with the 148/226 pair, in all likelihood because position 226 is on the opposite face of helix VII from position 228. Broadening of the electron paramagnetic resonance spectra in the frozen state was used to estimate distance between the 148/228 and the 148/275 pairs. The nitroxides at positions 148 and 228 or 148 and 275 are within approximately 13-15 A. Finally, Cys residues at positions 148 and 228 are crosslinked by dibromobimane, a bifunctional crosslinker that is approximately 5 A. long, while no crosslinking is detected between Cys residues at positions 148 and 275 or 148 and 226. The results provide strong support for a structure in which helix V is in close proximity to both helices VII and VIII and is oriented in such a fashion that Cys-148 is closer to helix VII.
ACESSO AO ARTIGO
http://www.pubmedcentral.nih.gov/articlerender.fcgi?artid=38347Documentos Relacionados
- Helix packing of lactose permease in Escherichia coli studied by site-directed chemical cleavage.
- Distance determination in proteins using designed metal ion binding sites and site-directed spin labeling: application to the lactose permease of Escherichia coli.
- A general method for determining helix packing in membrane proteins in situ: Helices I and II are close to helix VII in the lactose permease of Escherichia coli
- Site-Directed Spin-Labeling Study of the Light-Harvesting Complex CP29
- A transmembrane form of annexin XII detected by site-directed spin labeling