This model represents the large subunits of group of carbon-monoxide dehydrogenases that include molybdenum as part of the enzymatic cofactor. There are various forms of carbon-monoxide dehydrogenase; Salicibacter pomeroyi DSS-3, for example, has two forms. Note that, at least in some species, the active site Cys is modified with a selenium attached to (rather than replacing) the sulfur atom. This is termed selanylcysteine, and created post-translationally, in contrast to selenocysteine incorporation during translation as for many other selenoproteins. [Energy metabolism, Other]