Fig. 4: The structure of SspE_R100A and conformational changes in SspE.

a The structure of SspE_R100A was determined, and one of the four monomers in one asymmetric unit is displayed. b Structural superimposition of the wild-type SspE structure (slate) with SspE_R100A (cyan) to show that CTD exhibits en bloc movement toward the NTD. The DNA binding region of SspE_R100A is highlighted in red. The distance between the R404- and R408-containing helix and the NTD in SspE_R100A is greater than that in SspE. c The “open” and “closed” conformational states of SspE by normal mode analysis. The DNA binding region of SspE in the closed conformational state is highlighted in red. d A schematic representation describing the FRET changes of YFP-SspE-CFP in the closed-to-open transition. In the closed state, FRET occurs from excited CFP to YFP, leading to light emission from YFP at 530 nm. GTP hydrolysis causes a conformational change in SspE, leading to reduced emission from YFP and increased emission from CFP at 480 nm. e Spectra of FRET monitoring of YFP-SspE-CFP in vitro in the absence or presence of PT-DNA and/or GTP (left panel). FRET was expressed as the emission ratio of CFP to YFP signals (right panel). Data and error bars represent the mean ± SD from three independent experiments. Statistical significance was calculated by unpaired two-sided Student t tests; **P < 0.01, ***P < 0.001, and NS, not significant. f FRET analysis of YFP-SspE_K40A-CFP in vitro. FRET was reported as the emission ratio of CFP to YFP signals. Data and error bars represent the means ± SD from three independent experiments. Statistical significance was calculated by unpaired two-sided Student t tests; *P <  0.05, **P <  0.01, and NS, not significant. Source data are provided as a Source Data file.