@article {3338,
	title = {Modulation of biliverdin dynamics and spectral properties by Sandercyanin.},
	journal = {RSC Adv},
	volume = {12},
	year = {2022},
	month = {2022 Jul 06},
	pages = {20296-20304},
	abstract = {<p>Biliverdin IX-alpha (BV), a tetrapyrrole, is found ubiquitously in most living organisms. It functions as a metabolite, pigment, and signaling compound. While BV is known to bind to diverse protein families such as heme-metabolizing enzymes and phytochromes, not many BV-bound lipocalins (ubiquitous, small lipid-binding proteins) have been studied. The molecular basis of binding and conformational selectivity of BV in lipocalins remains unexplained. Sandercyanin (SFP)-BV complex is a blue lipocalin protein present in the mucus of the Canadian walleye (). In this study, we present the structures and binding modes of BV to SFP. Using a combination of designed site-directed mutations, X-ray crystallography, UV/VIS, and resonance Raman spectroscopy, we have identified multiple conformations of BV that are stabilized in the binding pocket of SFP. In complex with the protein, these conformers generate varied spectroscopic signatures both in their absorption and fluorescence spectra. We show that despite no covalent anchor, structural heterogeneity of the chromophore is primarily driven by the D-ring pyrrole of BV. Our work shows how conformational promiscuity of BV is correlated to the rearrangement of amino acids in the protein matrix leading to modulation of spectral properties.</p>
},
	issn = {2046-2069},
	doi = {10.1039/d2ra02880h},
	author = {Ghosh, Swagatha and Mondal, Sayan and Yadav, Keerti and Aggarwal, Shantanu and Schaefer, Wayne F and Narayana, Chandrabhas and Subramanian, Ramaswamy}
}
@article {1167,
	title = {Blue protein with red fluorescence.},
	journal = {Proc Natl Acad Sci U S A},
	volume = {113},
	year = {2016},
	month = {2016 10 11},
	pages = {11513-11518},
	abstract = {<p>The walleye (Sander vitreus) is a golden yellow fish that inhabits the Northern American lakes. The recent sightings of the blue walleye and the correlation of its sighting to possible increased UV radiation have been proposed earlier. The underlying molecular basis of its adaptation to increased UV radiation is the presence of a protein (Sandercyanin)-ligand complex in the mucus of walleyes. Degradation of heme by UV radiation results in the formation of Biliverdin IXα (BLA), the chromophore bound to Sandercyanin. We show that Sandercyanin is a monomeric protein that forms stable homotetramers on addition of BLA to the protein. A structure of the Sandercyanin-BLA complex, purified from the fish mucus, reveals a glycosylated protein with a lipocalin fold. This protein-ligand complex absorbs light in the UV region (λ of 375 nm) and upon excitation at this wavelength emits in the red region (λ of 675 nm). Unlike all other known biliverdin-bound fluorescent proteins, the chromophore is noncovalently bound to the protein. We provide here a molecular rationale for the observed spectral properties of Sandercyanin.</p>
},
	keywords = {Biliverdine, Crystallography, X-Ray, Fluorescence, Models, Molecular, Proteins, Recombinant Proteins},
	issn = {1091-6490},
	doi = {10.1073/pnas.1525622113},
	author = {Ghosh, Swagatha and Yu, Chi-Li and Ferraro, Daniel J and Sudha, Sai and Pal, Samir Kumar and Schaefer, Wayne F and Gibson, David T and Ramaswamy, S}
}
