Detection of a Yb3+ binding site in regenerated bacteriorhodopsin that is coordinated with the protein and phospholipid head groups

Proc Natl Acad Sci U S A. 1996 Dec 10;93(25):14333-7. doi: 10.1073/pnas.93.25.14333.


Near infrared Yb3+ vibronic sideband spectroscopy was used to characterize specific lanthanide binding sites in bacteriorhodopsin (bR) and retinal free bacteriorhodopsin (bO). The VSB spectra for deionized bO regenerated with a ratio of 1:1 and 2:1 ion to bO are identical. Application of a two-dimensional anti-correlation technique suggests that only a single Yb3+ site is observed. The Yb3+ binding site in bO is observed to consist of PO2- groups and carboxylic acid groups, both of which are bound in a bidentate manner. An additional contribution most likely arising from a phenolic group is also observed. This implies that the ligands for the observed single binding site are the lipid head groups and amino acid residues. The vibronic sidebands of Yb3+ in deionized bR regenerated at a ratio of 2:1 ion to bR are essentially identical to those in bO. The other high-affinity binding site is thus either not evident or its fluorescence is quenched. A discussion is given on the difference in binding of Ca2+ (or Mg2+) and lanthanides in phospholipid membrane proteins.

Publication types

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

MeSH terms

  • Bacteriorhodopsins / chemistry*
  • Bacteriorhodopsins / metabolism
  • Binding Sites
  • Metals, Rare Earth / chemistry*
  • Metals, Rare Earth / metabolism
  • Phospholipids / chemistry
  • Phospholipids / metabolism
  • Retinaldehyde
  • Spectroscopy, Near-Infrared


  • Metals, Rare Earth
  • Phospholipids
  • Bacteriorhodopsins
  • Retinaldehyde