title: Studies on nitrosyl hemes in Ni(II)-Fe(II) hybrid hemoglobins.
abstract: Subunit heterogeneity within a particular subunit in hemoglobin A have been explored with electron paramagnetic resonance spectroscopy using the nitrosyl hemes in Ni-Fe hybrid Hb under various solution conditions. Our previous studies on the crystal structure of NiHb demonstrated the presence of subunit heterogeneity within alpha-subunit. To further cross check this hypothesis, we made a hybrid Hb in which either the alpha- or beta-subunit contains iron, which alone can bind to NO. By this way dynamic exchange between penta- and hexa-coordinated forms within a subunit was confirmed. Upon the addition of inositol hexa phosphate (IHP) to these hybrids, R to T state transition is observed for [alpha(2)(Fe-NO)beta(2)(Ni)] but such a direct transformation is less marked in [alpha(2)(Ni)beta(2)(Fe-NO)]. Hence the bond between N(epsilon) and Fe is fundamental to the structure-function relation in Hb, as the motion of this nitrogen triggers the vast transformation, which occurs in the whole molecule on attachment of NO.
authors.affiliation: Department of Chemistry and Sophisticated Analytical Instrumentation Facility, Indian Institute of Technology, Madras, Chennai 600 036, India.
authors.forename: Swarnalatha
authors.initials: S
authors.lastname: Venkateshrao
authors.forename: Balan
authors.initials: B
authors.lastname: Venkatesh
authors.forename: Periakaruppan T
authors.initials: PT
authors.lastname: Manoharan
mesh_terms: D004578:Electron Spin Resonance Spectroscopy; D006418:Heme / Q000737:chemistry* / Q000378:metabolism*; D006454:Hemoglobins / Q000737:chemistry / Q000378:metabolism*; D006801:Humans; D007501:Iron / Q000378:metabolism*; D009532:Nickel / Q000378:metabolism*; D009584:Nitrogen / Q000737:chemistry*; D011993:Recombinant Fusion Proteins
chemical_list: D006454:Hemoglobins; D011993:Recombinant Fusion Proteins; C041823:hybrid hemoglobins; C008657:nitrosyl hemoglobin; D006418:Heme; D009532:Nickel; D007501:Iron; D009584:Nitrogen