2k78 | pdb_00002k78
Solution Structure of the IsdC NEAT domain bound to Zinc Protoporphyrin
Structural highlights
FunctionISDC_STAAW Involved in heme (porphyrin) scavenging. Binds hemoglobin and almost exclusively free-base protoporphyrin IX. Probably has a role as the central conduit of the isd heme uptake system, i.e. mediates the transfer of the iron-containing nutrient from IsdABH to the membrane translocation system IsdDEF (By similarity). Hemin-free IsdC (apo-IsdC) acquires hemin from hemin-containing IsdA (holo-IsdA) probably through the activated holo-IsdA-apo-IsdC complex and due to the higher affinity of apo-IsdC for the cofactor. The reaction is reversible.[1] Evolutionary Conservation Check, as determined by ConSurfDB. You may read the explanation of the method and the full data available from ConSurf. Publication Abstract from PubMedStaphylococcus aureus scavenges heme-iron from host hemoproteins using iron-regulated surface determinant (Isd) proteins. IsdC is the central conduit through which heme is passed across the cell wall and binds this molecule using a NEAr Transporter (NEAT) domain. NMR spectroscopy was used to determine the structure of IsdC in complex with a heme analog, zinc-substituted protoporphyrin IX (ZnPPIX). The backbone coordinates of the ensemble of conformers representing the structure exhibit a root mean square deviation to the mean structure of 0.53 +/- 0.11 angstroms. IsdC partially buries protoporphyrin within a large hydrophobic pocket that is located at the end of its beta-barrel structure. The central metal ion of the analog adopts a pentacoordinate geometry in which a highly conserved tyrosine residue serves as a proximal ligand. Consistent with the structure and its role in heme transfer across the cell wall, we show that IsdC weakly binds heme (K(D) = 0.34 +/- 0.12 microm) and that ZnPPIX rapidly dissociates from the protein at a rate of 126 +/- 30 s(-1). NMR studies of the apo-form of IsdC reveal that a 3(10) helix within the binding pocket undergoes a flexible to rigid transition as heme is captured. This structural plasticity may increase the efficiency of heme transfer across the cell wall by facilitating protein-protein interactions between apoIsdC and upstream hemoproteins. The IsdC protein from Staphylococcus aureus uses a flexible binding pocket to capture heme.,Villareal VA, Pilpa RM, Robson SA, Fadeev EA, Clubb RT J Biol Chem. 2008 Nov 14;283(46):31591-600. Epub 2008 Aug 20. PMID:18715872[2] From MEDLINE®/PubMed®, a database of the U.S. National Library of Medicine. References
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