Crystal Structure of Staphylococcus pseudintermedius SbnI in complex with ADP

Experimental Data Snapshot

  • Resolution: 1.90 Å
  • R-Value Free: 0.242 
  • R-Value Work: 0.207 
  • R-Value Observed: 0.209 

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The heme-sensitive regulator SbnI has a bifunctional role in staphyloferrin B production by Staphylococcus aureus .

Verstraete, M.M.Morales, L.D.Kobylarz, M.J.Loutet, S.A.Laakso, H.A.Pinter, T.B.Stillman, M.J.Heinrichs, D.E.Murphy, M.E.P.

(2019) J Biol Chem 294: 11622-11636

  • DOI: https://doi.org/10.1074/jbc.RA119.007757
  • Primary Citation of Related Structures:  
    5UJD, 6NR6

  • PubMed Abstract: 

    Staphylococcus aureus infection relies on iron acquisition from its host. S. aureus takes up iron through heme uptake by the iron-responsive surface determinant (Isd) system and by the production of iron-scavenging siderophores. Staphyloferrin B (SB) is a siderophore produced by the 9-gene sbn gene cluster for SB biosynthesis and efflux. Recently, the ninth gene product, SbnI, was determined to be a free l-serine kinase that produces O- phospho-l-serine (OPS), a substrate for SB biosynthesis. Previous studies have also characterized SbnI as a DNA-binding regulatory protein that senses heme to control sbn gene expression for SB synthesis. Here, we present crystal structures at 1.9-2.1 Å resolution of a SbnI homolog from Staphylococcus pseudintermedius (SpSbnI) in both apo form and in complex with ADP, a product of the kinase reaction; the latter confirmed the active-site location. The structures revealed that SpSbnI forms a dimer through C-terminal domain swapping and a dimer of dimers through intermolecular disulfide formation. Heme binding had only a modest effect on SbnI enzymatic activity, suggesting that its two functions are independent and structurally distinct. We identified a heme-binding site and observed catalytic heme transfer between a heme-degrading protein of the Isd system, IsdI, and SbnI. These findings support the notion that SbnI has a bifunctional role contributing precursor OPS to SB synthesis and directly sensing heme to control expression of the sbn locus. We propose that heme transfer from IsdI to SbnI enables S. aureus to control iron source preference according to the sources available in the environment.

  • Organizational Affiliation

    Department of Microbiology and Immunology, University of Western Ontario, London, Ontario N6A 5C1, Canada.

Find similar proteins by:  (by identity cutoff)  |  3D Structure
Entity ID: 1
MoleculeChains Sequence LengthOrganismDetailsImage
Bifunctional transcriptional regulator/O-phospho-L-serine synthase SbnI
A, B
254Staphylococcus pseudintermediusMutation(s): 0 
Gene Names: sbnIDD902_02060DD924_03760DV946_04660DV961_07520EGV54_05745
Find proteins for A0A166Q2C7 (Staphylococcus pseudintermedius)
Explore A0A166Q2C7 
Go to UniProtKB:  A0A166Q2C7
Entity Groups  
Sequence Clusters30% Identity50% Identity70% Identity90% Identity95% Identity100% Identity
UniProt GroupA0A166Q2C7
Sequence Annotations
  • Reference Sequence
Experimental Data & Validation

Experimental Data

  • Resolution: 1.90 Å
  • R-Value Free: 0.242 
  • R-Value Work: 0.207 
  • R-Value Observed: 0.209 
  • Space Group: P 21 21 2
Unit Cell:
Length ( Å )Angle ( ˚ )
a = 101.644α = 90
b = 73.074β = 90
c = 88.372γ = 90
Software Package:
Software NamePurpose
XDSdata reduction
Aimlessdata scaling
PDB_EXTRACTdata extraction

Structure Validation

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Entry History & Funding Information

Deposition Data

Funding OrganizationLocationGrant Number
Canadian Institutes of Health Research (CIHR)Canada49597
Canadian Institutes of Health Research (CIHR)Canada38002

Revision History  (Full details and data files)

  • Version 1.0: 2019-06-19
    Type: Initial release
  • Version 1.1: 2020-01-08
    Changes: Author supporting evidence
  • Version 1.2: 2020-12-30
    Changes: Database references, Derived calculations
  • Version 1.3: 2023-10-11
    Changes: Data collection, Database references, Refinement description