Site-directed isotope labelling and FTIR spectroscopy of bacteriorhodopsin

Sanjay Sonar, Chan Ping Lee, Matthew A Coleman, Nilam Patel, Xiaomei Liu, Thomas Marti, H. Gobind Khorana, Uttam L. RajBhandary, Kenneth J. Rothschild

Research output: Contribution to journalArticlepeer-review

69 Scopus citations


Insight into integral membrane proteins function is presently limited by the difficulty of producing three-dimensional crystals. In addition. X-ray structures of proteins normally do not provide information about the protonation state and structural changes of individual residues. We report here the first use of site-directed isotope labelling and Fourier transform infrared (FTIR) difference spectroscopy to detect structural changes at the level of single residues in an integral membrane protein. Two site-directed isotope labeled (SDIL) tyrosine analogues of bacteriorhodopsin were produced which exhibit normal activity. FTIR spectroscopy shows that out of 11 tyrosines, only Tyr 185 is structurally active during the early photocycle and may be part of a proton wire.

Original languageEnglish (US)
Pages (from-to)512-517
Number of pages6
JournalNature Structural Biology
Issue number8
StatePublished - Aug 1994
Externally publishedYes

ASJC Scopus subject areas

  • Biochemistry
  • Genetics
  • Structural Biology


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