May play a photoprotective role within PSI in response to light stress (PubMed:12805611). Forms a trimeric complex with OHP1 and HCF244 that is required to promote PSII core subunit assembly (PubMed:29930106, PubMed:30397023). The trimeric complex forms a transient PSII reaction center-like complex with PsbA, PsbD, PsbE, PsbF and PsbI subunits in thylakoids for early assembly of PSII as well as PSII repair (PubMed:30397023). The trimeric complex is required for the recruitment of ribosomes to the psbA mRNA during PSII biogenesis and repair (PubMed:31991763). Forms an heterodimer with OHP1 that binds chlorophylls and carotenoids, and that may function in the delivery of pigments to the PsbA subunit of PSII (PubMed:32071152). Component of a high molecular weight complex containing OHP1, OHP2 and HCF244, and PSII core proteins D1/D2, HCF136 and HCF173 (PubMed:29438089). Forms a trimeric complex with OHP1 and HCF244 that mutually stabilizes each subunit (PubMed:29930106, PubMed:30397023). Associates with PSI under low or high light conditions. Induced by exposure to high light. High light sensitivity leading to stunted growth with pale-green leaves on agar plates, but unable to grow on soil. Belongs to the ELIP/psbS family.