Murine Calprotectin Coordinates Mn(II) at a Hexahistidine Site with Ca(II)-Dependent Affinity
| Autor: | Elizabeth M. Nolan, Rose C. Hadley, Andrew Ozarowski, R. David Britt, Derek M. Gagnon |
|---|---|
| Rok vydání: | 2019 |
| Předmět: |
Coordination sphere
Stereochemistry chemistry.chemical_element Manganese 010402 general chemistry 01 natural sciences Article law.invention Coordination complex Metal Inorganic Chemistry Mice law Coordination Complexes Molecule Animals Humans Physical and Theoretical Chemistry Binding site Electron paramagnetic resonance chemistry.chemical_classification Binding Sites Molecular Structure 010405 organic chemistry Heterotetramer 0104 chemical sciences Infectious Diseases Emerging Infectious Diseases chemistry visual_art visual_art.visual_art_medium Calcium Inorganic & Nuclear Chemistry Infection Other Chemical Sciences Leukocyte L1 Antigen Complex Physical Chemistry (incl. Structural) |
| Zdroj: | Inorganic chemistry, vol 58, iss 20 Inorg Chem |
| Popis: | Manganese is an essential metal ion that bacterial pathogens need to acquire from the vertebrate host during infection. In the mammalian nutritional immunity strategy to combat bacterial infection, the host restricts bacterial access to Mn(II) by sequestering this metal nutrient using the protein calprotectin (CP). The role of murine calprotectin (mCP) in Mn(II) sequestration has been demonstrated in vivo, but the molecular basis of this function has not been evaluated. Herein, biochemical assays and electron paramagnetic resonance (EPR) spectroscopy are employed to characterize the Mn(II)-binding properties of mCP. We report that mCP has one high-affinity Mn(II)-binding site. This site is a His(6) site composed of His17 and His27 of mS100A8 and His92, His97, His105 and His107 of mS100A9. Similar to the human orthologue, Ca(II) binding to the EF-hand domains of mCP enhances the Mn(II) affinity of the protein; however, this effect requires ~10-fold more Ca(II) than what was previously observed for hCP. Mn(II) coordination to the His(6) site also promotes self-association of two mCP heterodimers to form a heterotetramer. Low-temperature X-band EPR spectroscopy revealed a nearly octahedral Mn(II) coordination sphere for the Mn(II)-His(6) site characterized by zero-field splitting (ZFS) parameters D = 525 MHz and E/D = 0.3. Further electron-nuclear double resonance (ENDOR) studies with globally (15)N-labeled mCP provided hyperfine couplings from the coordinating ε-nitrogen atoms of the His ligands (a(iso) = 4.3 MHz) as well as the distal δ-nitrogen atoms (a(iso) = 0.25 MHz). Mn(II)-competition assays between mCP and two bacterial Mn(II) solute-binding proteins, staphylococcal MntC and streptococcal PsaA showed that mCP outcompetes both proteins for Mn(II) under conditions of excess Ca(II). In total, this work provides the first coordination chemistry study of mCP and reveals striking similarities in the Mn(II) coordination sphere as well as notable differences in Ca(II) sensitivity and oligomerization behavior between hCP and mCP. |
| Databáze: | OpenAIRE |
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