title: Dehaloperoxidase-hemoglobin from Amphitrite ornata is primarily a monomer in solution.
abstract: The crystal structures of the dehaloperoxidase-hemoglobin from A. ornata (DHP A) each report a crystallographic dimer in the unit cell. Yet, the largest dimer interface observed is 450 Å(2), an area significantly smaller than the typical value of 1200-2000 Å(2) and in contrast to the extensive interface region of other known dimeric hemoglobins. To examine the oligomerization state of DHP A in solution, we used gel permeation by fast protein liquid chromatography and small-angle X-ray scattering (SAXS). Gel permeation experiments demonstrate that DHP A elutes as a monomer (15.5 kDa) and can be separated from green fluorescent protein, which has a molar mass of 27 kDa, near the 31 kDa expected for the DHP A dimer. By SAXS, we found that DHP A is primarily monomeric in solution, but with a detectable level of dimer (~10%), under all conditions studied up to a protein concentration of 3.0 mM. These concentrations are likely 10-100-fold lower than the K(d) for dimer formation. Additionally, there was no significant effect either on the overall conformation of DHP A or its monomer-dimer equilibrium upon addition of the DHP A inhibitor, 4-iodophenol.
authors.affiliation: Department of Chemistry, North Carolina State University, Raleigh, North Carolina 27695, USA.
authors.forename: Matthew K
authors.initials: MK
authors.lastname: Thompson
authors.forename: Stefan
authors.initials: S
authors.lastname: Franzen
authors.forename: Michael F
authors.initials: MF
authors.lastname: Davis
authors.forename: Ryan C
authors.initials: RC
authors.lastname: Oliver
authors.forename: Joanna K
authors.initials: JK
authors.lastname: Krueger
mesh_terms: D000818:Animals; D018360:Crystallography, X-Ray; D019281:Dimerization; D006454:Hemoglobins / Q000737:chemistry*; D010544:Peroxidases / Q000737:chemistry*; D011077:Polychaeta / Q000201:enzymology / Q000378:metabolism*; D011487:Protein Conformation; D053838:Scattering, Small Angle; D012996:Solutions / Q000737:chemistry; D014961:X-Ray Diffraction
chemical_list: D006454:Hemoglobins; D012996:Solutions; C098661:DHP I dehaloperoxidase; D010544:Peroxidases