image: Specimen of the glassfrog Espadarana callistomma from the tropical rainforests in the Chocó region of Ecuador. Large accumulations of a blue-green biliverdin binding serpin can be seen under the skin of the animals and are highly conspicuous in the humeral spines -osseous projections on the forelimbs- of the species. view more
Credit: Image credit: Santiago R. Ron
Proteins called biliverdin-binding serpins (BBSs) play an important role in amphibian coloration and camouflage, a study finds. Many vertebrates have blue-green blood and bones due to high concentrations of the pigment biliverdin. The biochemical basis and functions of this phenomenon, known as chlorosis, remain unclear. Carlos Taboada, Lucía Chemes, Sara Bari, and colleagues report that BBSs play an important role in amphibian chlorosis. Analysis of fluid samples from the amphibian species Boana punctata showed that BBSs are responsible for the frog's blue-green coloration. Amino acid sequencing and peptide analysis revealed that BBSs belong to the serpin superfamily of proteins, a large and ubiquitous group of protease inhibitors. The authors found high expression levels of BBSs in eight other chlorotic frog species analyzed. Additional experiments revealed that BBSs alter the spectral absorbance of biliverdin. Moreover, the absorbance spectrum of the visible band of BBSs partially overlaps B. punctata's reflectance spectra, which closely match those of native plants typically found near the frogs. Optical modeling showed that BBSs located in subcutaneous lymph and underlying connective tissue could fine-tune the frog's reflectance spectra, revealing a potential mechanism by which BBSs may affect crypsis. According to the authors, the study broadens the known functions of the serpin superfamily of proteins.
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Article #20-06771: "Multiple origins of green coloration in frogs mediated by a novel biliverdin-binding serpin," by Carlos Taboada et al.
MEDIA CONTACTS: Carlos Taboada, Duke University, Durham, NC; e-mail: <carlostaboada84@gmail.com>; Lucía Chemes, Fundacio?n Instituto Leloir and Instituto de Investigaciones Bioquímicas de Buenos Aires-CONICET, Buenos Aires, ARGENTINA; e-mail: <lchemes@iib.unsam.edu.ar>; Sara Bari, Universidad de Buenos Aires, Buenos Aires, ARGENTINA; e-mail: <bari@qi.fcen.uba.ar>
Journal
Proceedings of the National Academy of Sciences