3U2H:
reference: Structure of the surface layer of the methanogenic archaean Methanosarcina acetivorans., Arbing MA, Chan S, Shin A, Phan T, Ahn CJ, Rohlin L, Gunsalus RP, Proc Natl Acad Sci U S A. 2012 Jul 17;109(29):11812-7. Epub 2012 Jul 2. PMID: 22753492

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