The light-harvesting complex (LHC) functions as a light receptor, it captures and delivers excitation energy to photosystems with which it is closely associated. CP29 facilitates the State 1 to State 2 transition, where State I is induced by excess photosystem I (PSI) light and State 2 is induced by excess photosystem II (PSII) light. Binds at least 14 chlorophylls (8 Chl-a and 6 Chl-b) and carotenoids such as lutein and neoxanthin. The LHC complex consists of chlorophyll a-b binding proteins. Repressed by high light intensity due to a transient decrease in mRNA stability. Also down-regulated at lower light intensities by low temperature or limited carbon dioxide supply. 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. Reversible phosphorylation plays a role in the State transition process and determines the affinity of LHCII for PSI and PSII. Belongs to the light-harvesting chlorophyll a/b-binding (LHC) protein family.