title: Calcium Binding Dramatically Stabilizes an Ancestral Crystallin Fold in Tunicate βγ-Crystallin.
abstract: The tunicate (Ciona intestinalis) βγ-crystallin represents an intermediate case between the calcium-binding proteins ancestral to the vertebrate βγ-crystallin fold and the vertebrate structural crystallins. Unlike the structural βγ-crystallins in the vertebrate eye lens, this βγ-crystallin strongly binds Ca2+. Furthermore, Ca2+binding greatly stabilizes the protein, an effect that has previously been observed in microbial βγ-crystallins but not in those of vertebrates. This relationship between binding and protein stabilization makes the tunicate βγ-crystallin an interesting model for studying the evolution of the human βγ-crystallin. We also compare and contrast the binding sites of tunicate βγ-crystallin with those of other βγ-crystallins to develop hypotheses about the functional origin of the lack of Ca2+-binding sites in human crystallins.
authors.affiliation: Department of Chemistry, University of California , Irvine, California 92697-2025, United States.
authors.forename: Natalia
authors.initials: N
authors.lastname: Kozlyuk
authors.affiliation: Department of Chemistry, University of California , Irvine, California 92697-2025, United States.
authors.forename: Suvrajit
authors.identifier: http://orcid.org/0000-0002-9665-0088
authors.initials: S
authors.lastname: Sengupta
authors.affiliation: Department of Molecular Biology and Biochemistry, University of California , Irvine, California 92697-3900, United States.
authors.forename: Jan C
authors.initials: JC
authors.lastname: Bierma
authors.affiliation: Department of Chemistry, University of California , Irvine, California 92697-2025, United States.|Department of Molecular Biology and Biochemistry, University of California , Irvine, California 92697-3900, United States.
authors.forename: Rachel W
authors.identifier: http://orcid.org/0000-0001-9996-7411
authors.initials: RW
authors.lastname: Martin
mesh_terms: D000595:Amino Acid Sequence; D000818:Animals; D001665:Binding Sites; D002118:Calcium / Q000378:metabolism*; D002938:Ciona intestinalis / Q000378:metabolism*; D002942:Circular Dichroism; D019143:Evolution, Molecular; D006801:Humans; D007908:Lens, Crystalline / Q000378:metabolism*; D008958:Models, Molecular; D011487:Protein Conformation; D017386:Sequence Homology, Amino Acid; D013050:Spectrometry, Fluorescence; D038204:beta-Crystallins / Q000737:chemistry* / Q000378:metabolism; D038222:gamma-Crystallins / Q000737:chemistry* / Q000378:metabolism
chemical_list: D038204:beta-Crystallins; D038222:gamma-Crystallins; D002118:Calcium