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The crystal structure of EPD-BCP1 from a marine sponge
Structural highlights
Publication Abstract from PubMedMarine animals display diverse vibrant colors, but the mechanisms underlying their specific coloration remain to be clarified. Blue coloration is known to be achieved through a bathochromic shift of the orange carotenoid astaxanthin (AXT) by the crustacean protein crustacyanin, but other examples have not yet been well investigated. Here we identified an ependymin (EPD)-related water-soluble blue carotenoprotein responsible for the specific coloration of the marine blue sponge Haliclona sp. EPD was originally identified in the fish brain as a protein involved in memory consolidation and neuronal regeneration. The purified blue protein, designated as EPD-related blue carotenoprotein-1 (EPD-BCP1), was identified as a secreted glycoprotein. We show it consists of a heterodimer that binds orange AXT and mytiloxanthin (MXT) and exhibits a bathochromic shift. Our crystal structure analysis of the natively purified EPD-BCP1 revealed that these two carotenoids are specifically bound to the heterodimer interface, where the polyene chains are aligned in parallel to each other like in beta-crustacyanin, although the two proteins are evolutionary and structurally unrelated. Furthermore, using reconstitution assays, we found incomplete bathochromic shifts occurred when the protein bound to only AXT or MXT. Taken together, we identified an EPD in a basal metazoan as a blue protein that decorates the sponge body by binding specific structurally unrelated carotenoids. An ependymin-related blue carotenoprotein decorates marine blue sponge.,Kawasaki S, Kaneko T, Asano T, Maoka T, Takaichi S, Shomura Y J Biol Chem. 2023 Jul 28:105110. doi: 10.1016/j.jbc.2023.105110. PMID:37517696[1] From MEDLINE®/PubMed®, a database of the U.S. National Library of Medicine. References
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