Proximity of helices VIII (Ala273) and IX (Met299) in the lactose permease of Escherichia coli

Qingda Wang, John C Voss, Wayne L. Hubbell, H. Ronald Kaback

Research output: Contribution to journalArticle

19 Scopus citations

Abstract

Three double-Cys mutant pairs - Ala→273Cys/Met299→Cys, Thr266→Cys/Ile303→Cys, and Thr266→Cys/Ser306→Cys - were constructed in a functional lac permease construct devoid of Cys residues, and the excimer fluorescence or electron paramagnetic resonance (EPR) was studied with pyrene- or spin-labeled derivatives, respectively. After reconstitution into proteoliposomes, excimer fluorescence is observed with mutant Ala273→Cys/Met299→Cys, but not with the single-Cys mutants nor with mutants Thr266→Cys/Ile303→Cys or Thr266→Cys/Ser306→Cys. Furthermore, spin-spin interaction is also observed with mutant Ala273→Cys/Met299→Cys, but only after the permease is reconstituted into proteoliposomes. The results provide independent support for the conclusions that helix VIII is close to helix IX and that the transmembrane helices of the permease are more loosely packed in a detergent micelle as opposed to a phospholipid bilayer.

Original languageEnglish (US)
Pages (from-to)4910-4915
Number of pages6
JournalBiochemistry
Volume37
Issue number14
DOIs
StatePublished - Apr 7 1998

ASJC Scopus subject areas

  • Biochemistry

Fingerprint Dive into the research topics of 'Proximity of helices VIII (Ala273) and IX (Met299) in the lactose permease of Escherichia coli'. Together they form a unique fingerprint.

  • Cite this