A novel spectral tuning in the short wavelength-sensitive (SWS1 and SWS2) pigments of bluefin killifish (Lucania goodei)

• Authors: Shozo Yokoyama, Emory University; Naomi Takenaka, Emory University; Nathan Blow, Syracuse University
• Journal Title: Gene
• Volume: Volume 396, Number 1
• Publisher: Elsevier: 12 months | 2007-07-01, Pages 196-202
• Type of Work: Article | Post-print: After Peer Review
• Publisher DOI: http://doi.org/10.1016/j.gene.2007.03.019
• Subjects: Biology, Genetics; Biology, Oceanography
• Keywords: visual pigments; absorption spectra; mutagenesis; bluefin killifish

Abstract

The molecular bases of spectral tuning in the UV-, violet-, and blue-sensitive pigments are not well understood. Using the in vitro assay, here we show that the SWS1, SWS2-A, and SWS2-B pigments of bluefin killifish (Lucania goodei) have the wavelengths of maximal absorption (λmax’s) of 354, 448, and 397 nm, respectively. The spectral difference between the SWS2-A and SWS2-B pigments is largest among those of all currently known pairs of SWS2 pigments within a species. The SWS1 pigment contains no amino acid replacement at the currently known 25 critical sites and seems to have inherited its UV-sensitivity directly from the vertebrate ancestor. Mutagenesis analyses show that the amino acid differences at sites 44, 46, 94, 97, 109, 116, 118, 265, and 292 of the SWS2-A and SWS2-B pigments explain 80% of their spectral difference. Moreover, the larger the individual effects of amino acid changes on the λmax-shift are, the larger the synergistic effects tend to be generated, revealing a novel mechanism of spectral tuning of visual pigments.