Cell-free synthesis, functional refolding, and spectroscopic characterization of bacteriorhodopsin, an integral membrane protein

Biochemistry. 1993 Dec 21;32(50):13777-81. doi: 10.1021/bi00213a004.

Abstract

Bacteriorhodopsin (bR) is an integral membrane protein which functions as a light-driven proton pump in Halobacterium halobium (also known as Halobacterium salinarium). The cell-free synthesis of bR in quantities sufficient for FTIR and NMR spectroscopy and the ability to selectively isotope label bR using aminoacylated suppressor tRNAs would provide a powerful approach for studying the role of specific amino acid residues. However, no integral membrane protein has yet been expressed in a cell-free system in quantities sufficient for such biophysical studies. We report the cell-free synthesis of bacterioopsin, its purification, its refolding in polar lipids from H. halobium, and its regeneration with all-trans-retinal to yield bacteriorhodopsin in a form functionally similar to bR in purple membrane. Importantly, the yields obtained from in vitro and in vivo expression are comparable. Functionality of the cell-free expressed bR is established using static and time-resolved absorption spectroscopy and FTIR difference spectroscopy.

Publication types

  • Research Support, U.S. Gov't, Non-P.H.S.
  • Research Support, U.S. Gov't, P.H.S.

MeSH terms

  • Bacteriorhodopsins / biosynthesis*
  • Bacteriorhodopsins / chemistry
  • Bacteriorhodopsins / metabolism
  • Cell-Free System
  • Halobacterium salinarum / metabolism
  • Light
  • Magnetic Resonance Spectroscopy
  • Protein Folding*
  • Spectroscopy, Fourier Transform Infrared

Substances

  • Bacteriorhodopsins