02426nas a2200277   4500008004100000022001400041245011100055210006900166260009500235300001200330490000800342520139600350653002301746653001601769653001501785653001901800653004801819100002101867700002401888700002601912700002201938700001901960700002501979700002102004856012302025       2009                        eng d  a0006-291X00aConformational characterization of human eukaryotic initiation factor 2 alpha: a single tryptophan protein0 aConformational characterization of human eukaryotic initiation f  a525 B ST, STE 1900, SAN DIEGO, CA 92101-4495 USAbACADEMIC PRESS INC ELSEVIER SCIENCEcDEC  a273-2790 v3903 a<p>The alpha-subunit of the human eukaryotic initiation factor 2 (heIF2 alpha), a GTP binding protein, plays a major role in the initiation of protein synthesis. During various cytoplasmic stresses, eIF2 alpha gets phosphorylated by eIF2 alpha-specific kinases resulting in inhibition of protein synthesis. The cloned and over expressed heIF2 alpha, a protein with a single tryptophan (trp) residue was examined for its conformational characteristics using steady-state and time-resolved tryptophan fluorescence, circular dichroism (CD) and hydrophobic dye binding. The steady-state fluorescence spectrum, fluorescence lifetimes (tau(1) = 1.13 ns and tau(2) = 4.74 ns) and solute quenching studies revealed the presence of trp conformers in hydrophobic and differential polar environment at any given time. Estimation of the alpha-helix and beta-sheet content showed: (i) more compact structure at pH 2.0, (ii) distorted alpha-helix and rearranged beta-sheet in presence of 4 M guanidine hydrochloride and (iii) retention of more than 50% ordered structure at 95 degrees C. Hydrophobic dye binding to the protein with loosened tertiary structure was observed at pH 2.0 indicating the existence of a molten globule-like structure. These observations indicate the inherent structural stability of the protein under various denaturing conditions. (C) 2009 Elsevier Inc. All rights reserved.</p>10aCircular dichroism10aheIF2 alpha10aK562 cells10aMolten globule10aSteady-state and time-resolved fluorescence1 aSreejith, R., K.1 aYadav, Viveka, Nand1 aVarshney, Nishant, K.1 aBerwal, Sunil, K.1 aSuresh, C., G.1 aGaikwad, Sushama, M.1 aPal, Jayanta, K.  uhttps://library.ncl.res.in/content/conformational-characterization-human-eukaryotic-initiation-factor-2-alpha-single-002631nas a2200277   4500008004100000022001400041245015800055210006900213260007500282300001200357490000700369520154700376653002801923653002201951653002901973653001902002653004802021100002102069700001902090700002702109700002102136700001902157700002502176700002102201856013102222       2012                        eng d  a1053-050900aConformational transitions of the catalytic domain of heme-regulated eukaryotic initiation factor 2 alpha kinase, a key translational regulatory molecule0 aConformational transitions of the catalytic domain of hemeregula  a233 SPRING ST, NEW YORK, NY 10013 USAbSPRINGER/PLENUM PUBLISHERScJAN  a431-4410 v223 a<p>In mammalian cells, the heme-regulated inhibitor (HRI) plays a critical role in the regulation of protein synthesis at the initiation step through phosphorylation of a-subunit of the eukaryotic initiation factor 2 (eIF2). In this study we have cloned and performed biophysical characterization of the kinase catalytic domain (KD) of rabbit HRI. The KD described here comprises kinase 1, the kinase insertion domain (KI) and kinase 2. We report here the existence of an active and stable monomer of HRI (KD). The HRI (KD) containing three tryptophan residues was examined for its conformational transitions occurring under various denaturing conditions using steady-state and time-resolved tryptophan fluorescence, circular dichroism (CD) and hydrophobic dye binding. The parameter A and phase diagram analysis revealed multi-state unfolding and existence of three stable intermediates during guanidine hydrochloride (Gdn-HCl) induced unfolding of HRI (KD). The protein treated with 6 M Gdn-HCl showed collisional and static mechanism of acrylamide quenching and the constants (K-sv=3.08 M-1 and K-s=5.62 M-1) were resolved using time resolved fluorescence titration. Based on pH, guanidine hydrochloride and temperature mediated transitions, HRI (KD) appears to exemplify a rigid molten globule-like intermediate with compact secondary structure, altered tertiary structure and exposed hydrophobic patches at pH 3.0. The results indicate the inherent structural stability of HRI (KD), a member of the class of stress response proteins.</p>10aCircular dichroism (CD)10aeIF2 alpha kinase10aHeme-regulated inhibitor10aMolten globule10aSteady-state and time-resolved fluorescence1 aSreejith, R., K.1 aSuresh, C., G.1 aBhosale, Siddharth, H.1 aBhavnani, Varsha1 aKumar, Avinash1 aGaikwad, Sushama, M.1 aPal, Jayanta, K.  uhttps://library.ncl.res.in/content/conformational-transitions-catalytic-domain-heme-regulated-eukaryotic-initiation-factor-2-0