Estimation of thermodynamic stability of human carbonic anhydrase IX from urea-induced denaturation and MD simulation studies

Danish Idrees, Safikur Rahman, Mohd Shahbaaz, Md Anzarul Haque, Asimul Islam, Faizan Ahmad, Md Imtaiyaz Hassan

Research output: Contribution to journalArticlepeer-review


Carbonic anhydrase IX (CAIX) is a transmembrane glycoprotein, overexpressed in cancer cells under hypoxia condition. In cancerous cells, CAIX plays an important role to combat the deleterious effects of a high rate of glycolytic metabolism. In order to favor tumor survival, CAIX maintains intracellular pH neutral or slightly alkaline and extracellular acidic pH. The equilibrium unfolding and conformational stability of CAIX were measured in the presence of increasing urea concentrations to understand it's structural features under stressed conditions. Two different spectroscopic techniques were used to follow urea-induced denaturation and observed that urea induces a reversible denaturation of CAIX. Coincidence of the normalized transition curves of both optical properties suggesting that denaturation of CAIX is a two-state process, i.e., native state ↔ denatured state. Each denaturation curve was analyzed to estimate thermodynamic parameters, ΔGD0,value of Gibbs free energy change (ΔGD) associated with the urea-induced denaturation, Cm (midpoint of denaturation) and m (= δΔGD/δ[urea]). We further performed molecular dynamics simulation of CAIX for 50 ns to see the dynamics of protein structure in the presence of different urea concentrations. An excellent agreement was observed between in silico and in vitro studies.

Original languageEnglish (US)
Pages (from-to)183-189
Number of pages7
JournalInternational Journal of Biological Macromolecules
StatePublished - Dec 2017
Externally publishedYes


  • Human carbonic anhydrase IX
  • Molecular dynamics and simulation
  • Protein folding
  • Protein stability
  • Urea-induced denaturation

ASJC Scopus subject areas

  • Structural Biology
  • Biochemistry
  • Molecular Biology
  • Economics and Econometrics
  • General Energy


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