title: The native state of apomyoglobin described by proton NMR spectroscopy: the A-B-G-H interface of wild-type sperm whale apomyoglobin.
abstract: Proton nuclear magnetic resonance spectroscopy was applied to sperm whale apomyoglobin to describe the conformation adopted by the protein under native conditions. The study focused on the A-B-G-H interface, a region known to form a compact subdomain in the apoprotein (Hughson and Baldwin, Biochemistry 28:4415-4422, 1989). Two histidine residues located in this subdomain, His24 and His119, interact and are thought to play a role in the acid denaturation process (Barrick et al., J. Mol. Biol. 237:588-601, 1994). A stable double mutant at these positions (His24Val/His119Phe sperm whale apomyoglobin) was compared with wild-type apomyoglobin. The amino acid replacements result in chemical shift perturbations near the mutations, in particular in the AB interhelical region, and in a deceleration of backbone amide hydrogen exchange in the B helix from position 27 to position 33. The double mutant data were used to expand and confirm the wild-type spectral analysis. Signals from the D helix were identified that demonstrate the formation of holoprotein-like structure. The assigned wild-type nuclear Overhauser effects, although in small number, were sufficient to construct a model of the compact subdomain of the apoprotein. This was achieved by using the structure of the holoprotein and restraining it with the geometrical information on the apoprotein in a simulated annealing procedure. The experimental restraints define a low-resolution model of the A-B-G-H interface in apomyoglobin.
authors.affiliation: Department of Chemistry, Pennsylvania State University, University Park 16802, USA.
authors.forename: J T
authors.initials: JT
authors.lastname: Lecomte
authors.forename: Y H
authors.initials: YH
authors.lastname: Kao
authors.forename: M J
authors.initials: MJ
authors.lastname: Cocco
mesh_terms: D000818:Animals; D001059:Apoproteins / Q000737:chemistry* / Q000235:genetics; D009682:Magnetic Resonance Spectroscopy; D009154:Mutation; D009211:Myoglobin / Q000737:chemistry* / Q000235:genetics; D011487:Protein Conformation; D011522:Protons; D014907:Whales
chemical_list: D001059:Apoproteins; D009211:Myoglobin; D011522:Protons; C010857:apomyoglobin