This family is found in Bacteria and Streptophyta includes members such as NdhS (NAD(P)H-quinone oxidoreductase subunit S). NdhS, also known as CRR31 (chlororespiratory reduction 31), is a subunit of the chloroplast NADH dehydrogenase-like (NDH) complex. It is also a subunit of the cyanobacterial NDH-1 complex. NAD(P)H-oxidizing subunits have not been found in chloroplasts or cyanobacteria, where ferredoxin is probably the electron donor. NdhS contributes to the formation of a ferredoxin binding site of NDH and is necessary for high affinity binding of ferredoxin. The cyanobacterial NDH-1 complex, also known as NADPH:plastoquinone oxidoreductase or type I NAD(P)H dehydrogenase, is involved in plastoquinone reduction and cyclic electron transfer (CET) around photosystem I. The chloroplast NDH is more similar to cyanobacterial NDH-1, which is believed to be the origin of chloroplast NDH, than to mitochondrial NADH dehydrogenase present in the same species. The NDH complexes of chloroplasts, however, contain many subunits that are absent from cyanobacterial NDH-1 complexes.