Structural and Functional Consequences of the Weak Binding of Chlorin e6 to Bovine Rhodopsin

James Mitchell, Naveena Yanamala, Yi Lei Tan, Eric E. Gardner, Kalyan C. Tirupula, Fernanda Balem, Mordechai Sheves, Daniel Nietlispach, Judith Klein-Seetharaman

Research output: Contribution to journalArticlepeer-review

3 Scopus citations


The chlorophyll-derivative chlorin e6 (Ce6) identified in the retinas of deep-sea ocean fish is proposed to play a functional role in red bioluminescence detection. Fluorescence and 1 H NMR spectroscopy studies with the bovine dim-light photoreceptor, rhodopsin, indicate that Ce6 weakly binds to it with μm affinity. Absorbance spectra prove that red light sensitivity enhancement is not brought about by a shift in the absorbance maximum of rhodopsin. 19 F NMR experiments with samples where 19 F labels are either placed at the cytoplasmic binding site or incorporated as fluorinated retinal indicate that the cytoplasmic domain is highly perturbed by binding, while little to no changes are detected near the retinal. Binding of Ce6 also inhibits G-protein activation. Chemical shift changes in 1 H- 15 N NMR spectroscopy of 15 N-Trp labeled bovine rhodopsin reveal that Ce6 binding perturbs the entire structure. These results provide experimental evidence that Ce6 is an allosteric modulator of rhodopsin.

Original languageEnglish (US)
Pages (from-to)787-802
Number of pages16
JournalPhotochemistry and photobiology
Issue number3
StatePublished - May 1 2019
Externally publishedYes

ASJC Scopus subject areas

  • Biochemistry
  • Physical and Theoretical Chemistry


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