Members of this family are predominantly found in prokaryotic D-lactate dehydrogenase, forming the cap-membrane-binding domain, which consists of a large seven-stranded antiparallel beta-sheet flanked on both sides by alpha-helices. They allow for membrane association [1].

1: The crystal structure of D-lactate dehydrogenase, a peripheral membrane respiratory enzyme. Dym O, Pratt EA, Ho C, Eisenberg D; Proc Natl Acad Sci U S A. 2000;97:9413-9418. PMID:10944213