title: Divalent metal ion complexes of S100B in the absence and presence of pentamidine.
abstract: As part of an effort to inhibit S100B, structures of pentamidine (Pnt) bound to Ca(2+)-loaded and Zn(2+),Ca(2+)-loaded S100B were determined by X-ray crystallography at 2.15 A (R(free)=0.266) and 1.85 A (R(free)=0.243) resolution, respectively. These data were compared to X-ray structures solved in the absence of Pnt, including Ca(2+)-loaded S100B and Zn(2+),Ca(2+)-loaded S100B determined here (1.88 A; R(free)=0.267). In the presence and absence of Zn(2+), electron density corresponding to two Pnt molecules per S100B subunit was mapped for both drug-bound structures. One Pnt binding site (site 1) was adjacent to a p53 peptide binding site on S100B (+/-Zn(2+)), and the second Pnt molecule was mapped to the dimer interface (site 2; +/-Zn(2+)) and in a pocket near residues that define the Zn(2+) binding site on S100B. In addition, a conformational change in S100B was observed upon the addition of Zn(2+) to Ca(2+)-S100B, which changed the conformation and orientation of Pnt bound to sites 1 and 2 of Pnt-Zn(2+),Ca(2+)-S100B when compared to Pnt-Ca(2+)-S100B. That Pnt can adapt to this Zn(2+)-dependent conformational change was unexpected and provides a new mode for S100B inhibition by this drug. These data will be useful for developing novel inhibitors of both Ca(2+)- and Ca(2+),Zn(2+)-bound S100B.
authors.affiliation: Department of Biochemistry and Molecular Biology, The University of Maryland School of Medicine, 108 North Greene Street, Baltimore, MD 21201, USA.
authors.forename: Thomas H
authors.initials: TH
authors.lastname: Charpentier
authors.forename: Paul T
authors.initials: PT
authors.lastname: Wilder
authors.forename: Melissa A
authors.initials: MA
authors.lastname: Liriano
authors.forename: Kristen M
authors.initials: KM
authors.lastname: Varney
authors.forename: Edwin
authors.initials: E
authors.lastname: Pozharski
authors.forename: Alexander D
authors.initials: AD
authors.lastname: MacKerell
authors.forename: Andrew
authors.initials: A
authors.lastname: Coop
authors.forename: Eric A
authors.initials: EA
authors.lastname: Toth
authors.forename: David J
authors.initials: DJ
authors.lastname: Weber
mesh_terms: D000818:Animals; D002118:Calcium / Q000378:metabolism*; D002417:Cattle; D018360:Crystallography, X-Ray; D007700:Kinetics; D009682:Magnetic Resonance Spectroscopy; D008958:Models, Molecular; D009414:Nerve Growth Factors / Q000737:chemistry / Q000378:metabolism*; D010419:Pentamidine / Q000737:chemistry / Q000378:metabolism*; D017433:Protein Structure, Secondary; D051381:Rats; D064568:S100 Calcium Binding Protein beta Subunit; D009418:S100 Proteins / Q000737:chemistry / Q000378:metabolism*; D013816:Thermodynamics; D015032:Zinc / Q000378:metabolism*
chemical_list: D009414:Nerve Growth Factors; D064568:S100 Calcium Binding Protein beta Subunit; D009418:S100 Proteins; C579158:S100b protein, rat; D010419:Pentamidine; D015032:Zinc; D002118:Calcium