TY - JOUR T1 - A phylogenetically diverse class of “blind” type 1 opsins JF - bioRxiv DO - 10.1101/033027 SP - 033027 AU - Erin A. Becker AU - Andrew I. Yao AU - Phillip M. Seitzer AU - Tobias Kind AU - Ting Wang AU - Rich Eigenheer AU - Katie S. Y. Shao AU - Vladimir Yarov-Yarovoy AU - Marc T. Facciotti Y1 - 2015/01/01 UR - http://biorxiv.org/content/early/2015/11/26/033027.abstract N2 - Opsins are photosensitive proteins catalyzing light-dependent processes across the tree of life. For both microbial (type 1) and metazoan (type 2) opsins, photosensing depends upon covalent interaction between a retinal chromophore and a conserved lysine residue. Despite recent discoveries of potential opsin homologs lacking this residue, phylogenetic dispersal and functional significance of these abnormal sequences have not yet been investigated. We report discovery of a large group of putatively non-retinal binding opsins, present in a number of fungal and microbial genomes and comprising nearly 30% of opsins in the Halobacteriacea, a model clade for opsin photobiology. Based on phylogenetic analyses, structural modeling, genomic context and biochemistry, we propose that these abnormal opsin homologs represent a novel family of sensory opsins which may be involved in taxis response to one or more non-light stimuli. This finding challenges current understanding of microbial opsins as a light-specific sensory family, and provides a potential analogy with the highly diverse signaling capabilities of the eukaryotic G-protein coupled receptors (GPCRs), of which metazoan type 2 opsins are a light-specific sub-clade. ER -