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1xyd
From Proteopedia
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NMR Solution Structure of Rat Zinc-Calcium-S100B, 20 Structures
Overview
The EF-hand calcium-binding protein S100B also binds one zinc ion per, subunit with a relatively high affinity (K(d) approximately 90 nM) [Wilder, et al., (2003) Biochemistry 42, 13410-13421]. In this study, the, structural characterization of zinc binding to calcium-loaded S100B was, examined using high-resolution NMR techniques, including structural, characterization of this complex in solution at atomic resolution. As with, other S100 protein structures, the quaternary structure of, Zn(2+)-Ca(2+)-bound S100B was found to be dimeric with helices H1, H1', H4, and H4' forming an X-type four-helix bundle at the dimer interface., NMR data together with mutational analyses are consistent with Zn(2+), coordination arising from His-15 and His-25 of one S100B subunit and from, His-85 and Glu-89 of the other subunit. The addition of Zn(2+) was also, found to extend helices H4 and H4' three to four residues similar to what, was previously observed with the binding of target proteins to S100B., Furthermore, a kink in helix 4 was observed in Zn(2+)-Ca(2+)-bound S100B, that is not in Ca(2+)-bound S100B. These structural changes upon, Zn(2+)-binding could explain the 5-fold increase in affinity that, Zn(2+)-Ca(2+)-bound S100B has for peptide targets such as the TRTK peptide, versus Ca(2+)-bound S100B. There are also changes in the relative, positioning of the two EF-hand calcium-binding domains and the respective, helices comprising these EF-hands. Changes in conformation such as these, could contribute to the order of magnitude higher affinity that S100B has, for calcium in the presence of Zn(2+).
About this Structure
1XYD is a Single protein structure of sequence from Rattus norvegicus with CA and ZN as ligands. Full crystallographic information is available from OCA.
Reference
Solution structure of zinc- and calcium-bound rat S100B as determined by nuclear magnetic resonance spectroscopy., Wilder PT, Varney KM, Weiss MB, Gitti RK, Weber DJ, Biochemistry. 2005 Apr 19;44(15):5690-702. PMID:15823027
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