Required for both formation and activity of the chloroplast NAD(P)H dehydrogenase (NDH) complex. Subunit of the lumenal protuberance of the NDH complex. Associated with the chloroplast NAD(P)H dehydrogenase/photosystem I (NDH/PSI) supercomplex. Impaired chloroplastic NAD(P)H dehydrogenase (NDH) activity, probably due to a reduced stability of the NDH complex. Belongs to the psbQ family.