Molecular Dynamics Simulation To Investigate The Impact Of Disulfide Bond Formation On Structure Stability Of Cystatin Mononer

Alzheimer's disease and Cerebral amyloid angiopathy caused by cystatin amyloid mutant amyloid aggregation in the human body.The reason is the L68Q mutantogenic is the causative agent of Human cystatin C amyloid angiopathy(HCCAA).Appendant structure(AS)chicken cystatin(cC)has highly homology with Human cystatin C(HCC),It has already been verified that it is more feasible,economical and convenient to study the amyloidogenic properties as well as its biological activities by using cC instead of HCC.To date,3D domain swapping has been observed in more than 30 different proteins,our group demonstrated that the hydrophobic core region and AS play an important role in the whole time course of the domain swapping.Disulfide bond and salt bridge formation have been identified as specific interactions that can stabilize aggregation-prone interfaces in native protein con formations and thus prevent structural rearrangements that are required for misfolding and aggregation A previous study by Bjork and Ylinenjarvi showed that the Cys95-Cys115 disulfide bond,but not the Cys71-Cys81 bond of cC,is of more importance for maintaining the native conformation of cC and is crucial for its proteinase-binding ability.The formation of disulfide bonds has been associated with stabilizing interaction between protein secondary structures.This led us to investigate the impact of disulfide bond formation on structure stability Properties of cystatin mononer.In this article,we have studied wild-type cystatin WT?natural mutant I66Q?new mutant I108T respectively and investigate the impact of disulfide bond Cys71-Cys81 and Cys95-Cys115 formation on structure stability Properties of cystatin monomer Ours data suggest that the AS domain and disulfide bridge Cys71-Cys81 have a higher propensity for structural perturbation than the the protein region harboring the Cys95-Cys115 disulfide bond.Furthermore.the breakage of the Cys95-Cys115 disulfide bond has a high impact on the cystatin's unfolding process and may play a major role in triggering domain swapping and dimerization.Further analysis of the structural change in various reduced states of the mononer confirmed that the decrease a-helical content is mainly be breakage of the much more highly accessible Cys71-Cys81 and Cys95-Cysll5 disulfide bond would have a greater impact on protein unfolding due to disruption of Helix 2 and therefore displacement of the AS region.In summary,we suggest that this difference may represent a key factor in the cystatin to undergo unfolding process.Further experimental and computational studies on the relationship between disulfide bond formations with a variety of cystatin will provide valuable insight and help elucidate the possible direct and indirect influence of disulfide bond status on domain swapping,dimerization,and amyloid fibril formation of the cystatins.These results might help to reveal the possible role of important residues in the process of cystatin domain swapping and also provide potent clues for exploring the potential critical domains in domain swapping associated with hydrophobic core.