May play a photoprotective role in the thylakoid membrane in response to light stress (Probable). Involved in photosystems I (PSI) and II (PSII) core proteins function (PubMed:29438089). Forms a trimeric complex with OHP2 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). May bind chlorophyll and form dimers in the thylakoid membrane (Probable). Component of a high molecular weight complex containing OHP1, OHP2 and HCF244, and PSII core proteins D1/D2, HCF136 and HCF173 (PubMed:29438089). Interacts with HCF244 (PubMed:29438089) (Probable). Forms a trimeric complex with OHP2 and HCF244 that mutually stabilizes each subunit (PubMed:29930106, PubMed:30397023). Associated with both photosystems I and II. Mostly expressed in cotyledons and shoot apices. Highly expressed in seedling cotyledons and shoot apices in young and mature plants. Induced by exposure to high light (PubMed:10794534, PubMed:29438089, PubMed:30489183). Expression follows circadian diurnal fluctuations with highest levels before and shortly after the light phase (PubMed:10794534). High light sensitivity leading to stunted growth with pale-green leaves on agar plates, but unable to grow on soil (PubMed:29438089). Impaired photosystem II (PSII) core protein function and reduced levels of photosystem I core proteins (PubMed:29438089). Belongs to the ELIP/psbS family.