Fig. 4: EsaDc-EsaG may form tetramer through CF.

a Native mass spectrum of EsaDc-EsaG complex at low (10 µM) and high (50 µM) concentrations. Experimental molecular weights for dimer and tetramer calculated based on the assigned charge states are 39.092 KD (theoretical molecular weight 38.764 KD) and 77.789 KD (theoretical molecular weight 77.528 KD), respectively. b Ribbon representation of EsaDc-EsaG heterodimer interacting with nearby asymmetric units. The proteins are colored in the same scheme as shown in Fig. 1a. Potential dimer-to-dimer interfaces across the crystal unit cells are presented as black dash. Close-up view of the residues selected for cross-linking are highlighted below. c SDS-PAGE analysis of EsaG and EsaDc variants incubated with the IA probe. The experiments were performed twice with similar results. d ¹⁹F-NMR spectra of EsaDc-¹⁹F-W567 in the presence of different equivalents of EsaG. Black lines are the experimental spectra, blue lines are deconvoluted peaks and magenta lines are the sum of deconvoluted peaks. e–g are the spectra (left) of EsaDc¹⁹F-W567 mixed with the indicated equivalent of EsaG and 50 mM Ga-DTPA-BMA. The cartoon representations (right) are the solvent accessibility of the ¹⁹F-W567 in free EsaDc, corresponding to P1 (e), in EsaDc-EsaG dimer, corresponding to P2 (f), and in EsaDc-EsaG tetramer, corresponding to P3 (g), respectively. The sPRE strengths in Hz are indicated under the cartoons.