Mutation-Induced Deamidation of Corneal Dystrophy-Related Transforming Growth Factor β-Induced Protein

Biochemistry. 2017 Dec 12;56(49):6470-6480. doi: 10.1021/acs.biochem.7b00668. Epub 2017 Nov 22.


Mutations in the transforming growth factor β-induced protein (TGFBIp) cause phenotypically diverse corneal dystrophies, where protein aggregation in the cornea leads to severe visual impairment. Previous studies have shown a relationship between mutant-specific corneal dystrophy phenotypes and the thermodynamic stability of TGFBIp. Using liquid chromatography-tandem mass spectrometry and nuclear magnetic resonance (NMR), we investigated correlations between the structural integrity of disease-related mutants of the fourth FAS1 domain (FAS1-4) and deamidation of TGFBIp residue Asn622. We observed a high rate of Asn622 deamidation in the A546D and A546D/P551Q FAS1-4 mutants that were both largely unstructured as determined by NMR. Conversely, the more structurally organized A546T and V624M FAS1-4 mutants had reduced deamidation rates, suggesting that a folded and stable FAS1-4 domain precludes Asn622 deamidation. Wild-type, R555Q, and R555W FAS1-4 mutants displayed very slow deamidation, which agrees with their similar and ordered NMR structures, where Asn622 is in a locked conformation. We confirmed the FAS1-4 mutational effect on deamidation rates in full-length TGFBIp mutants and found a similar ranking compared to that of the FAS1-4 domain alone. Consequently, the deamidation rate of Asn622 can be used to predict the structural effect of the many destabilizing and/or stabilizing mutations reported for TGFBIp. In addition, the deamidation of Asn622 may influence the pathophysiology of TGFBIp-induced corneal dystrophies.

MeSH terms

  • Cornea / metabolism
  • Corneal Dystrophies, Hereditary / genetics*
  • Corneal Dystrophies, Hereditary / metabolism
  • Extracellular Matrix Proteins / chemistry
  • Extracellular Matrix Proteins / genetics*
  • Extracellular Matrix Proteins / metabolism*
  • Humans
  • Kinetics
  • Mutation*
  • Protein Domains
  • Protein Processing, Post-Translational
  • Transforming Growth Factor beta / chemistry
  • Transforming Growth Factor beta / genetics*
  • Transforming Growth Factor beta / metabolism*


  • Extracellular Matrix Proteins
  • Transforming Growth Factor beta
  • betaIG-H3 protein