6UTC:
reference: A disulfide constrains the ToxR periplasmic domain structure, altering its interactions with ToxS and bile-salts., Midgett CR, Swindell RA, Pellegrini M, Jon Kull F, Sci Rep. 2020 Jun 2;10(1):9002. doi: 10.1038/s41598-020-66050-5. PMID: 32488093

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