Fujimoto Zui, Kishine Naomi, Saitou Kengo, Kimura Keitarou
Research Center for Advanced Analysis, National Agriculture and Food Research Organization, 2-1-2 Kannondai, Tsukuba, Ibaraki 305-8518, Japan.
Institute of Food Research, National Agriculture and Food Research Organization, 2-1-12 Kannondai, Tsukuba, Ibaraki 305-8548, Japan.
Acta Crystallogr F Struct Biol Commun. 2025 Oct 1;81(Pt 10):425-433. doi: 10.1107/S2053230X25007903. Epub 2025 Sep 12.
Bacillus subtilis DegQ is a 46-amino-acid regulatory protein involved in the DegS-DegU two-component system. DegQ promotes the phosphorylation of DegU by DegS, switching the function of DegU from competence to the induction of poly-γ-glutamate production. To elucidate its structural role, we determined the crystal structures of wild-type DegQ and its mutant DegQS25L. Each DegQ monomer folds into a single α-helix, and four monomers assemble into a tetramer characterized by a four-helix coiled-coil structure. Within the tetramer, two adjacent helices are oriented in the same direction, while the other two are oriented oppositely, forming a pseudo-twofold symmetric arrangement. The mutant form displays disrupted symmetry due to altered helix packing, which is caused by shifts in the coiled-coil heptad register induced by the mutation. Structural predictions using AlphaFold3 suggest that DegQ likely binds to the N-terminal helix bundle of DegS, either as a dimer or as individual monomers. These findings provide structural insight into DegQ oligomerization and its potential role in modulating DegS autophosphorylation and DegU binding.
