Native MS showing recapitulation of the EthR6-DNA complex from two independent half-sites. MS spectra of a) EthR and DNAL31 in a 6:1 ratio, showing formation of mainly EthR2-DNA complex, and b) EthR and DNAR31 in a 6:1 ratio, showing formation of mainly EthR4-DNA complex, along with a small amount of EthR2-DNA and EthR3-DNA complexes. c) When EthR was mixed with both DNAL31 and DNAR31, a small amount of the putative EthR6-DNAL31-DNAR31 complex was formed.