The interaction of L-Cys with α-Chymotrypsin: Molecular Dynamic simulation and spectroscopic methods

L-Cysteine (L-Cys) is one of 20 α-amino acids, which connected by peptide and disulfide bonds in proteins and polypeptides. The L-Cys plays a very considerable role in stabilization of protein structure at a higher level due to disulfide bridges. The interaction of small chemical molecules, such as drugs to proteins has been very much considered in recent years. Distinguishing the thermodynamic and kinetic properties of α-Chymotrypsin (α-Chy) helps us for understanding this protein. For investigating the effect of L-Cys on structure and activity of α-Chy, spectroscopic and computational approaches were used. The UV–Vis results are revealed that the most absorption peaks were found at 260–300 nm due to Trp residues. Hyperchromism shift was seen in the presence of L-Cys. This was because of the forming of the ground state complex between α-Chy and L-Cys. Static quenching was seen by emission intensity changes. The more polar environment for Trp residue was recommended by the fluorescence quenching. The secondary structure alterations were slight. A reduce in the content of β-sheet structure and an increase in the a-helix were shown. Kinetic parameters display that L-Cys inhibited the activity of the enzyme by a mixed mod. Molecular docking results show a negative value for the Gibbs free energy of the binding of L-Cys to α-Chy with hydrophobic interactions. The molecular dynamic simulation revealed α-Chy becomes more stable in the presence of L-Cys.

کلیدواژه ها:

L-Cysteine ، α-Chymotrypsin ، Circular dichroism ، Fluorescence quenching ، Molecular dynamic simulation