title: Solution structure of the QUA1 dimerization domain of pXqua, the Xenopus ortholog of Quaking.
abstract: The STAR protein family member Quaking is essential for early development in vertebrates. For example, in oligodendrocyte cells it regulates the splicing, localization, translation and lifetime of a set of mRNAs that code for crucial components of myelin. The Quaking protein contains three contiguous conserved regions: a QUA1 oligomerization element, followed by a single-stranded RNA binding motif comprising the KH and QUA2 domains. An embryonic lethal point mutation in the QUA1 domain, E48G, is known to affect both the aggregation state and RNA-binding properties of the murine Quaking ortholog (QKI). Here we report the NMR solution structure of the QUA1 domain from the Xenopus laevis Quaking ortholog (pXqua), which forms a dimer composed of two perpendicularly docked α-helical hairpin motifs. Size exclusion chromatography studies of a range of mutants demonstrate that the dimeric state of the pXqua QUA1 domain is stabilized by a network of interactions between side-chains, with significant roles played by an intra-molecular hydrogen bond between Y41 and E72 (the counterpart to QKI E48) and an inter-protomer salt bridge between E72 and R67. These results are compared with recent structural and mutagenesis studies of QUA1 domains from the STAR family members QKI, GLD-1 and Sam68.
authors.affiliation: Department of Biochemistry, University of Cambridge, Cambridge, United Kingdom.
authors.forename: Muzaffar
authors.initials: M
authors.lastname: Ali
authors.forename: R William
authors.initials: RW
authors.lastname: Broadhurst
mesh_terms: D048868:Adaptor Proteins, Signal Transducing / Q000737:chemistry / Q000235:genetics / Q000378:metabolism; D020816:Amino Acid Motifs; D019943:Amino Acid Substitution; D000818:Animals; D006860:Hydrogen Bonding; D009682:Magnetic Resonance Spectroscopy; D051379:Mice; D020125:Mutation, Missense; D055503:Protein Multimerization / Q000502:physiology*; D017434:Protein Structure, Tertiary; D016601:RNA-Binding Proteins / Q000737:chemistry* / Q000235:genetics / Q000378:metabolism; D029867:Xenopus Proteins / Q000737:chemistry* / Q000235:genetics / Q000378:metabolism; D014982:Xenopus laevis
chemical_list: D048868:Adaptor Proteins, Signal Transducing; C513253:Khdrbs1 protein, mouse; C490830:QKI protein, Xenopus; C098217:Qk protein, mouse; D016601:RNA-Binding Proteins; D029867:Xenopus Proteins