title: A nuclear overhauser study of heme orientational isomerism in monomeric Chironomus hemoglobins.
abstract: The nuclear Overhauser effect (NOE) was used to investigate heme orientation and to obtain assignments for all resolved resonances in the 1H-NMR spectrum of met-cyano Chironomus thummi thummi monomeric hemoglobins III and IV (Hb III and Hb IV). The only non-heme resolved resonance was found to be from Phe-38 (CD1), and NOE dipolar connectivity between this resonance and the heme 5- and 8-methyls was used to establish the absolute orientation of the heme for each heme-insertion isomer present. The assignments of resonances and heme disorder permitted structural comparisons between the various components, including those due to a point mutation in Hb III. Finally, the characteristic differences of NOE patterns to amino-acid protons from substituents on heme pyrroles I and II formed the basis for assigning resonances and heme orientation relative to native Hb IV for deuterohemin-reconstituted Hb IV, for which there are no X-ray data available.
authors: Department of Chemistry, University of California, Davis 95616.
authors: D H
authors: DH
authors: Peyton
authors: G N
authors: GN
authors: La Mar
authors: K
authors: K
authors: Gersonde
mesh_terms: D000818:Animals; D002683:Chironomidae; D006418:Heme; D006454:Hemoglobins; D007536:Isomerism; D009682:Magnetic Resonance Spectroscopy; D011487:Protein Conformation
chemical_list: D006454:Hemoglobins; D006418:Heme