The light-harvesting complex (LHC) functions as a light receptor, it captures and delivers excitation energy to photosystems with which it is closely associated, here photosystem I. Binds at least 14 chlorophylls (8 Chl-a and 6 Chl-b) and carotenoids such as lutein and neoxanthin. Emission maxima at 735 nm. The LHC complex consists of chlorophyll a-b binding proteins (PubMed:19139095, PubMed:17476261). Red-emitting heterodimer with LHCA2 (PubMed:17107674, PubMed:21083539). Interacts with LHCA5 (PubMed:15356385). Binds to carotenoids (PubMed:17326666). Induced by low light (LL) but repressed by high light (HL). Inhibited by cold. The N-terminus of the protein extends into the stroma where it is involved with adhesion of granal membranes and post-translational modifications; both are believed to mediate the distribution of excitation energy between photosystems I and II. Photoregulated by reversible phosphorylation of its threonine residues. Slight decrease (30 percent) of LHCA2 levels (at protein level). Light emission at 715-720 nm upon excitation at 440 and 475 nm, and subsequent transfer of excitation energy to the photosystem I core with a relative slow rate of 25 nsec(-1). Belongs to the light-harvesting chlorophyll a/b-binding (LHC) protein family.