Plays a key role in regulating the relative amounts of cyclic and non-cyclic electron flow to meet the demands of the plant for ATP and reducing power. H(+) + NADP(+) + 2 reduced [2Fe-2S]-[ferredoxin] = NADPH + 2 oxidized [2Fe-2S]-[ferredoxin] Energy metabolism; photosynthesis. Heterodimer with LFNR2 (By similarity). Component of high molecular weight thylakoid LFNRs-containing protein complexes containing LIR1, LFNR1, LFNR2, TIC62 and TROL proteins. Interacts directly with LFNR1 and LFNR2; LIR1 increases the affinity of LFNR1 and LFNR2 for TIC62 and subsequent thylakoid relocalization (By similarity). May form interchain disulfide bonds with LIR1. Belongs to the ferredoxin--NADP reductase type 1 family.