title: Triphosphate induced dimerization of human guanylate binding protein 1 involves association of the C-terminal helices: a joint double electron-electron resonance and FRET study.
abstract: Human guanylate binding protein 1 (hGBP1) is a member of the dynamin superfamily of large GTPases. During GTP hydrolysis, the protein undergoes structural changes leading to self-assembly. Previous studies have suggested dimerization of the protein by means of its large GTPase (LG) domain and significant conformational changes in helical regions near the LG domain and at its C-terminus. We used site-directed labeling and a combination of pulsed electron paramagnetic resonance and time-resolved fluorescence spectroscopy for structural investigations on hGBP1 dimerization and conformational changes of its C-terminal helix α13. Consistent distance measurements by double electron-electron resonance (DEER, also named pulse double electron resonance = PELDOR) spectroscopy and Förster resonance energy transfer (FRET) measurements using model-free analysis approaches revealed a close interaction of the two α13 helices in the hGBP1 dimer formed upon binding of the nonhydrolyzable nucleoside triphosphate derivate GppNHp. In molecular dynamics (MD) simulations, these two helices form a stable dimer in solution. Our data show that dimer formation of hGBP1 involves multiple spatially distant regions of the protein, namely, the N-terminal LG domain and the C-terminal helices α13. The contacts formed between the two α13 helices and the resulting juxtaposition are expected to be a key step for the physiological membrane localization of hGBP1 through the farnesyl groups attached to the end of α13.
authors.affiliation: Physical Chemistry I, Faculty of Chemistry and Biochemistry, Ruhr-University Bochum , Universitätsstrasse 150, 44780 Bochum, Germany.
authors.forename: Tobias
authors.initials: T
authors.lastname: Vöpel
authors.forename: Carola S
authors.initials: CS
authors.lastname: Hengstenberg
authors.forename: Thomas-Otavio
authors.initials: TO
authors.lastname: Peulen
authors.forename: Yathrib
authors.initials: Y
authors.lastname: Ajaj
authors.forename: Claus A M
authors.initials: CA
authors.lastname: Seidel
authors.forename: Christian
authors.initials: C
authors.lastname: Herrmann
authors.forename: Johann P
authors.initials: JP
authors.lastname: Klare
mesh_terms: D031541:Fluorescence Resonance Energy Transfer; D019204:GTP-Binding Proteins / Q000737:chemistry* / Q000235:genetics; D006801:Humans; D055503:Protein Multimerization; D020836:Protein Structure, Quaternary; D017433:Protein Structure, Secondary; D017434:Protein Structure, Tertiary
chemical_list: C490287:GBP1 protein, human; D019204:GTP-Binding Proteins