Structure-function studies of the Bacillus subtilis Ric proteins identify the Fe-S cluster-litigating residues and their roles in development and RNA processing
Khaja, Faisal Tarique
Jeffrey, Philip D.
Neiditch, Matthew B.
American Society for Microbiology
In Bacillus subtilis, the RicA (YmcA), RicF (YlbF), and RicT (YaaT) proteins accelerate the phosphorylation of the transcription factor Spo0A, contributing to ge netic competence, sporulation, and biofilm formation, and are also essential for the correct maturation of several protein-encoding and riboswitch RNAs. These proteins form a stable complex (RicAFT) that carries two [4Fe-4S] 2 clusters. We show here that the complex is a 1:1:1 heterotrimer, and we present the X-ray crystal structures of a RicAF heterotetramer and of a RicA dimer. We also demonstrate that one of the Fe-S clusters (cluster 1) is ligated by cysteine residues donated exclusively by RicT and can be retained when the RicT monomer is purified by itself. Cluster 2 is ligated by C167 from RicT, by C134 and C146 located near the C terminus of RicF, and by C141 at the C terminus of RicA. These findings imply the following novel arrange ment: adjacent RicT residues C166 and 167 ligate clusters 1 and 2, respectively, while cluster 2 is ligated by cysteine residues from RicT, RicA, and RicF. Thus, the two clusters must lie close to one another and at the interface of the RicAFT protomers. We also show that the cluster-ligating cysteine residues, and therefore most likely both Fe-S clusters, are essential for cggR-gapA mRNA maturation, for the regulation of ricF transcript stability, and for several Ric-associated developmental phenotypes, including competence for transformation, biofilm formation, and sporu lation. Finally, we present evidence that RicAFT, RicAF, and RicA and the RicT mono mer may play distinct regulatory roles in vivo.
Open access article. Creative Commons Attribution 4.0 International LIcense (CC BY 4.0) applies
Ric proteins , Iron sulfur cluster , RNA processing , Bacterial development , Fe-S cluster
Adusei-Danso, F., Khaja, F. T., DeSantis, M., Jeffrey, P. D., Dubnau, E., Demeler, B., Neiditch, M. B., & Dubnau, D. (2019). Structure-function studies of the Bacillus subtilis Ric proteins identify the Fe-S cluster-litigating residues and their roles in development and RNA processing. mBio, 10(5), Article e01841-19. https://doi.org/10.1128/mBio.01841-19