title: 1H resonance assignments and secondary structure of the carbon monoxide complex of soybean leghemoglobin determined by homonuclear two-dimensional and three-dimensional NMR spectroscopy.
abstract: Homonuclear two-dimensional and three-dimensional 1H-NMR spectroscopy has been utilized to study the 15.9-kDa protein soybean leghemoglobin. NMR experiments were performed on the diamagnetic carbon monoxide complex at two temperatures and two pH values. Sequence-specific assignments have been made for 94% of the backbone and approximately 70% of the expected side-chain resonances. The secondary structure of leghemoglobin in solution has been determined on the basis of NOE connectivity patterns, hydrogen exchange and chemical-shift analyses. Leghemoglobin consists of seven helices and, unlike mammalian myoglobins, is missing the D helix. Instead an extended loop, the CE loop, is observed which might have importance for ligand entry into and exit from the protein interior. The hydrogen exchange behavior for the F helix and at the beginning of the A helix suggests different dynamic stability compared to other helical regions in leghemoglobin. Population of a second protein conformation, in which there is perturbation at the A-G-H helix interface, is observed at low pH.
authors.affiliation: Department of Molecular Biology, Scripps Research Institute, La Jolla, CA 92037.
authors.forename: D
authors.initials: D
authors.lastname: Morikis
authors.forename: C A
authors.initials: CA
authors.lastname: Lepre
authors.forename: P E
authors.initials: PE
authors.lastname: Wright
mesh_terms: D000595:Amino Acid Sequence; D002248:Carbon Monoxide / Q000378:metabolism*; D006859:Hydrogen; D007874:Leghemoglobin / Q000737:chemistry* / Q000378:metabolism*; D009682:Magnetic Resonance Spectroscopy / Q000379:methods; D008958:Models, Molecular; D008969:Molecular Sequence Data; D010649:Phenylalanine; D011487:Protein Conformation; D017433:Protein Structure, Secondary; D013025:Glycine max / Q000378:metabolism*
chemical_list: D007874:Leghemoglobin; D010649:Phenylalanine; D002248:Carbon Monoxide; D006859:Hydrogen