02052nas a2200241   4500008004100000245015300041210006900194260000800263300000900271490000700280520119100287653003501478653002301513653003001536653002001566100001701586700001601603700001701619700001601636700001501652700001201667856013101679       2017                        eng d00aElucidation of molecular mechanism of stability of the heme-regulated eIF2α kinase upon binding of its ligand, hemin in its catalytic kinase domain0 aElucidation of molecular mechanism of stability of the hemeregul  cSEP  a1-170 v353 aThe eIF2α kinase activity of the heme-regulated inhibitor (HRI) is regulated by heme which makes it a unique member of the family of eIF2α kinases. Since heme concentrations create an equilibrium for the kinase to be active/inactive, it becomes important to study the heme binding effects upon the kinase and understanding its mechanism of functionality. In the present study, we report the thermostability achieved by the catalytic kinase domain of HRI (HRI.CKD) upon ligand (heme) binding. Our CD data demonstrates that the HRI.CKD retains its secondary structure at higher temperatures when it is in ligand bound state. HRI.CKD when incubated with hemin loses its monomeric state and attains a higher order oligomeric form resulting in its stability. The HRI.CKD fails to refold into its native conformation upon mutation of H377A/H381A, thereby confirming the necessity of these His residues for correct folding, stability, and activity of the kinase. Though our in silico study demonstrated these His being the ligand binding sites in the kinase insert region, the spectra-based study did not show significant difference in heme affinity for the wild type and His mutant HRI.CKD.10aHeme Regulated Inhibitor (HRI)10aHRI-eIF2α Complex10aProtein–Ligand Modeling10aThermostability1 aBhavnani, V.1 aKaviraj, S.1 aPanigrahi, P1 aSuresh, C.G1 aYapara, S.1 aPal, J.  uhttps://library.ncl.res.in/content/elucidation-molecular-mechanism-stability-heme-regulated-eif2%CE%B1-kinase-upon-binding-its