4KGH

Crystal Structure of human splunc1 lacking the secretion signal sequence


Experimental Data Snapshot

  • Method: X-RAY DIFFRACTION
  • Resolution: 2.806 Å
  • R-Value Free: 0.295 
  • R-Value Work: 0.246 

wwPDB Validation 3D Report Full Report


This is version 1.2 of the entry. See complete history

Literature

Molecular basis for pH-dependent mucosal dehydration in cystic fibrosis airways.

Garland, A.L.Walton, W.G.Coakley, R.D.Tan, C.D.Gilmore, R.C.Hobbs, C.A.Tripathy, A.Clunes, L.A.Bencharit, S.Stutts, M.J.Betts, L.Redinbo, M.R.Tarran, R.

(2013) Proc.Natl.Acad.Sci.USA 110: 15973-15978

  • DOI: 10.1073/pnas.1311999110
  • Primary Citation of Related Structures:  

  • PubMed Abstract: 
  • The ability to maintain proper airway surface liquid (ASL) volume homeostasis is vital for mucus hydration and clearance, which are essential aspects of the mammalian lung's innate defense system. In cystic fibrosis (CF), one of the most common life- ...

    The ability to maintain proper airway surface liquid (ASL) volume homeostasis is vital for mucus hydration and clearance, which are essential aspects of the mammalian lung's innate defense system. In cystic fibrosis (CF), one of the most common life-threatening genetic disorders, ASL dehydration leads to mucus accumulation and chronic infection. In normal airways, the secreted protein short palate lung and nasal epithelial clone 1 (SPLUNC1) effectively inhibits epithelial Na(+) channel (ENaC)-dependent Na(+) absorption and preserves ASL volume. In CF airways, it has been hypothesized that increased ENaC-dependent Na(+) absorption contributes to ASL depletion, and hence increased disease. However, this theory is controversial, and the mechanism for abnormal ENaC regulation in CF airways has remained elusive. Here, we show that SPLUNC1 is a pH-sensitive regulator of ENaC and is unable to inhibit ENaC in the acidic CF airway environment. Alkalinization of CF airway cultures prevented CF ASL hyperabsorption, and this effect was abolished when SPLUNC1 was stably knocked down. Accordingly, we resolved the crystal structure of SPLUNC1 to 2.8 Å. Notably, this structure revealed two pH-sensitive salt bridges that, when removed, rendered SPLUNC1 pH-insensitive and able to regulate ASL volume in acidic ASL. Thus, we conclude that ENaC hyperactivity is secondary to reduced CF ASL pH. Together, these data provide molecular insights into the mucosal dehydration associated with a range of pulmonary diseases, including CF, and suggest that future therapy be directed toward alkalinizing the pH of CF airways.


    Organizational Affiliation

    Cystic Fibrosis/Pulmonary Research and Treatment Center, Department of Chemistry, Department of Biochemistry and Biophysics, Departments of Prosthodontics and Pharmacology, Department of Microbiology and Immunology, and Department of Cell Biology and Physiology, University of North Carolina, Chapel Hill, NC 27599.




Macromolecules

Find similar proteins by: Sequence  |  Structure

Entity ID: 1
MoleculeChainsSequence LengthOrganismDetails
BPI fold-containing family A member 1
B, A
240Homo sapiensMutation(s): 0 
Gene Names: BPIFA1 (LUNX, NASG, PLUNC, SPLUNC1, SPURT)
Find proteins for Q9NP55 (Homo sapiens)
Go to Gene View: BPIFA1
Go to UniProtKB:  Q9NP55
Small Molecules
Ligands 4 Unique
IDChainsName / Formula / InChI Key2D Diagram3D Interactions
NA
Query on NA

Download SDF File 
Download CCD File 
B
SODIUM ION
Na
FKNQFGJONOIPTF-UHFFFAOYSA-N
 Ligand Interaction
GOL
Query on GOL

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Download CCD File 
B
GLYCEROL
GLYCERIN; PROPANE-1,2,3-TRIOL
C3 H8 O3
PEDCQBHIVMGVHV-UHFFFAOYSA-N
 Ligand Interaction
NH4
Query on NH4

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Download CCD File 
B
AMMONIUM ION
H4 N
QGZKDVFQNNGYKY-UHFFFAOYSA-O
 Ligand Interaction
NO3
Query on NO3

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Download CCD File 
B
NITRATE ION
N O3
NHNBFGGVMKEFGY-UHFFFAOYSA-N
 Ligand Interaction
Experimental Data & Validation

Experimental Data

  • Method: X-RAY DIFFRACTION
  • Resolution: 2.806 Å
  • R-Value Free: 0.295 
  • R-Value Work: 0.246 
  • Space Group: C 2 2 21
Unit Cell:
Length (Å)Angle (°)
a = 47.475α = 90.00
b = 203.727β = 90.00
c = 118.612γ = 90.00
Software Package:
Software NamePurpose
PHASERphasing
SCALEPACKdata scaling
PDB_EXTRACTdata extraction
DENZOdata reduction
PHENIXrefinement
RESOLVEphasing

Structure Validation

View Full Validation Report or Ramachandran Plots



Entry History 

Deposition Data

Revision History 

  • Version 1.0: 2013-09-25
    Type: Initial release
  • Version 1.1: 2013-10-09
    Type: Database references
  • Version 1.2: 2017-11-15
    Type: Refinement description