| Title | Crystal structure of Streptomyces coelicolor RraAS2, an unusual member of the RNase E inhibitor RraA protein family |
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| Author | Nohra Park1, Jihune Heo2, Saemee Song1, Inseong Jo1, Kangseok Lee2*, and Nam-Chul Ha1* |
| Address | 1Department of Agricultural Biotechnology, Center for Food Safety and Toxicology, Research Institute for Agriculture and Life Sciences, Seoul National University, Seoul 08826, Republic of Korea, 2Department of Life Science, Chung-Ang University, Seoul 06974, Republic of Korea |
| Bibliography | Journal of Microbiology, 55(5),388-395, 2017, |
| DOI | 10.1007/s12275-017-7053-8 |
| Key Words | Rnase ES inhibitor, crystal structure, Streptomyces coelicolor |
| Abstract | Bacterial ribonuclease E (RNase E) plays a crucial role in the processing and decay of RNAs. A small protein named RraA negatively regulates the activity of RNase E via protein-protein interaction in various bacteria. Recently, RraAS1 and RraAS2, which are functional homologs of RraA from Escherichia coli, were identified in the Gram-positive species Streptomyces coelicolor. RraAS1 and RraAS2 inhibit RNase ES ribonuclease activity in S. coelicolor. RraAS1 and RraAS2 have a C-termi-nal extension region unlike typical bacterial RraA proteins. In this study, we present the crystal structure of RraAS2, ex-hibiting a hexamer arranged in a dimer of trimers, consistent with size exclusion chromatographic results. Importantly, the C-terminal extension region formed a long α-helix at the junction of the neighboring subunit, which is similar to the trimeric RraA orthologs from Saccharomyces cerevisiae. Trun-cation of the C-terminal extension region resulted in loss of RNase ES inhibition, demonstrating its crucial role. Our find-ings present the first bacterial RraA that has a hexameric assembly with a C-terminal extension α-helical region, which plays an essential role in the regulation of RNase ES activity in S. coelicolor. |