title: Structure, binding interface and hydrophobic transitions of Ca2+-loaded calbindin-D(28K).
abstract: Calbindin-D(28K) is a Ca2+-binding protein, performing roles as both a calcium buffer and calcium sensor. The NMR solution structure of Ca2+-loaded calbindin-D(28K) reveals a single, globular fold consisting of six distinct EF-hand subdomains, which coordinate Ca2+ in loops on EF1, EF3, EF4 and EF5. Target peptides from Ran-binding protein M and myo-inositol monophosphatase, along with a new target from procaspase-3, are shown to interact with the protein on a surface comprised of alpha5 (EF3), alpha8 (EF4) and the EF2-EF3 and EF4-EF5 loops. Fluorescence experiments reveal that calbindin-D(28K) adopts discrete hydrophobic states as it binds Ca2+. The structure, binding interface and hydrophobic characteristics of Ca2+-loaded calbindin-D(28K) provide the first detailed insights into how this essential protein may function. This structure is one of the largest high-resolution NMR structures and the largest monomeric EF-hand protein to be solved to date.
authors.affiliation: Department of Molecular and Structural Biochemistry, North Carolina State University, Raleigh, North Carolina 27695, USA.
authors.forename: Douglas J
authors.initials: DJ
authors.lastname: Kojetin
authors.forename: Ronald A
authors.initials: RA
authors.lastname: Venters
authors.forename: David R
authors.initials: DR
authors.lastname: Kordys
authors.forename: Richele J
authors.initials: RJ
authors.lastname: Thompson
authors.forename: Rajiv
authors.initials: R
authors.lastname: Kumar
authors.forename: John
authors.initials: J
authors.lastname: Cavanagh
mesh_terms: D000595:Amino Acid Sequence; D000818:Animals; D001665:Binding Sites; D064026:Calbindins; D002118:Calcium / Q000378:metabolism*; D003001:Cloning, Molecular; D006860:Hydrogen Bonding; D009682:Magnetic Resonance Spectroscopy; D008958:Models, Molecular; D010455:Peptides / Q000737:chemistry; D017510:Protein Folding; D017433:Protein Structure, Secondary; D051381:Rats; D011994:Recombinant Proteins / Q000737:chemistry / Q000378:metabolism; D064030:S100 Calcium Binding Protein G / Q000737:chemistry* / Q000378:metabolism*
chemical_list: D064026:Calbindins; D010455:Peptides; D011994:Recombinant Proteins; D064030:S100 Calcium Binding Protein G; D002118:Calcium