The solution structure of Sr33 coiled-coil domain challenges paradigms for coiled-coil dimerization in plant NLR immune receptors.
A. BENTHAM (1), L. Casey (2), P. Lavrencic (2), P. Anderson (1), B. Kobe (2), S. Williams (2) (1) Flinders University, Australia; (2) University of Queensland, Australia

two structures of coiled-coil (CC) domains from plant CC-NLR proteins, Mla10 from Hordeum vulgare and Rx from Solanum tuberosum, have been elucidated. Despite belonging to the same subclass of CC domains, the published structures of the Mla10 and Rx CC domains display two vastly different conformations. Mla10 CC domain forms a helix-loop-helix in an anti-parallel homodimer, whereas Rx CC domain adopts a monomeric four-helix bundle. In this study we present the NMR structure of the CC domain of the wheat CC-NLR, Sr33. We also report an in-solution biophysical analysis of the Sr33, Mla10, and Rx CC domains, using small angle x-ray scattering and multi-angle light scattering coupled with size-exclusion chromatography. We demonstrate the CC domains of Sr33, Mla10 and Rx are all monomeric, and all adopt a four-helix bundle fold in solution. Further biophysical and functional characterisation of extended CC domain constructs leads to the redefinition of minimal functional unit of the CC domain.

Abstract Number: P18-659
Session Type: Poster