In vitro and in silico studies of urea-induced denaturation of yeast iso-1-cytochrome c and its deletants at pH 6.0 and 25 °c

Md Anzarul Haque, Sobia Zaidi, Shah Ubaid-Ullah, Amresh Prakash, Md Imtaiyaz Hassan, Asimul Islam, Janendra K. Batra, Faizan Ahmad

Research output: Contribution to journalArticlepeer-review

31 Scopus citations

Abstract

Yeast iso-1-cytochrome c (y-cyt-c) has five extra residues at N-terminus in comparison to the horse cytochrome c. These residues are numbered as -5 to -1. Here, these extra residues are sequentially removed from y-cyt-c to establish their role in folding and stability of the protein. We performed urea-induced denaturation of wild-type (WT) y-cyt-c and its deletants. Denaturation was followed by observing change in Δε405 (probe for measuring change in the heme environment within the protein), [θ]405 (probe for measuring the change in Phe82 and Met80 axial bonding), [θ]222 (probe for measuring change in secondary structure) and [θ]416 (probe for measuring change in the heme-methionine environment). The urea-induced reversible denaturation curves were used to estimate Δ, the value of Gibbs free energy change (ΔGD0) in the absence of urea; Cm, the midpoint of the denaturation curve, i.e. molar urea concentration ([urea]) at which ΔGD = 0; and m, the slope (=∂ΔGD/∂[urea]). Our in vitro results clearly show that except Δ(-5/-4) all deletants are less stable than WT protein. Coincidence of normalized transition curves of all physical properties suggests that unfolding/refolding of WT protein and its deletants is a two-state process. To confirm our in vitro observations, we performed 40 ns MD simulation of both WT y-cyt-c and its deletants. MD simulation results clearly show that extra N-terminal residues play a role in stability but not in folding of the protein.

Original languageEnglish (US)
Pages (from-to)1493-1502
Number of pages10
JournalJournal of Biomolecular Structure and Dynamics
Volume33
Issue number7
DOIs
StatePublished - Jul 3 2015
Externally publishedYes

Keywords

  • molecular dynamics and simulation
  • protein folding
  • protein stability
  • two-state unfolding
  • urea denaturation
  • yeast iso-1-cytochrome c

ASJC Scopus subject areas

  • Structural Biology
  • Molecular Biology

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