This domain represents the N-terminal of NAD(P)H-quinone oxidoreductase subunit 2 (or subunit B), part of the P-module (pumping) of the photosynthetic complex I from plants and cyanobacteria, which is structurally and functionally related to the respiratory complex I from mitochondria and bacteria. It is involved in the electron transfer between photosynthetic complex I and photosystem I [1].

1: Structural adaptations of photosynthetic complex I enable ferredoxin-dependent electron transfer. Schuller JM, Birrell JA, Tanaka H, Konuma T, Wulfhorst H, Cox N, Schuller SK, Thiemann J, Lubitz W, Setif P, Ikegami T, Engel BD, Kurisu G, Nowaczyk MM; Science. 2019;363:257-260. PMID:30573545