title: Kinetic asymmetry of subunit exchange of homooligomeric protein as revealed by deuteration-assisted small-angle neutron scattering.
abstract: We developed a novel, to our knowledge, technique for real-time monitoring of subunit exchange in homooligomeric proteins, using deuteration-assisted small-angle neutron scattering (SANS), and applied it to the tetradecamer of the proteasome α7 subunit. Isotopically normal and deuterated tetradecamers exhibited identical SANS profiles in 81% D(2)O solution. After mixing these solutions, the isotope sensitive SANS intensity in the low-q region gradually decreased, indicating subunit exchange, whereas the small-angle x-ray scattering profile remained unchanged confirming the structural integrity of the tetradecamer particles during the exchange. Kinetic analysis of zero-angle scattering intensity indicated that 1), only two of the 14 subunits were exchanged in each tetradecamer and 2), the exchange process involves at least two steps. This study underscores the usefulness of deuteration-assisted SANS, which can provide quantitative information not only on the molecular sizes and shapes of homooligomeric proteins, but also on their kinetic properties.
authors: Research Reactor Institute, Kyoto University, Kumatori, Osaka, Japan. sugiyama@rri.kyoto-u.ac.jp
authors: Masaaki
authors: M
authors: Sugiyama
authors: Eiji
authors: E
authors: Kurimoto
authors: Hirokazu
authors: H
authors: Yagi
authors: Kazuhiro
authors: K
authors: Mori
authors: Toshiharu
authors: T
authors: Fukunaga
authors: Mitsuhiro
authors: M
authors: Hirai
authors: Giuseppe
authors: G
authors: Zaccai
authors: Koichi
authors: K
authors: Kato
mesh_terms: D003903:Deuterium / Q000737:chemistry*; D006801:Humans; D007700:Kinetics; D008958:Models, Molecular; D033363:Neutron Diffraction; D046988:Proteasome Endopeptidase Complex / Q000737:chemistry* / Q000378:metabolism; D055503:Protein Multimerization; D020836:Protein Structure, Quaternary; D021122:Protein Subunits / Q000737:chemistry* / Q000378:metabolism; D053838:Scattering, Small Angle
chemical_list: D021122:Protein Subunits; D003903:Deuterium; C488662:PSMA7 protein, human; D046988:Proteasome Endopeptidase Complex