Auxiliary factor required, together with HCF173, for the biogenesis of photosystem II (PSII), especially for the synthesis of the reaction center proteins (e.g. D1), via the regulation of the corresponding mRNA (e.g. psbA) translation initiation (ribosomal loading) and stabilization (PubMed:29930106). Forms a trimeric complex with OHP1 and OHP2 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). Component of a high molecular weight complex containing OHP1, OHP2 and HCF244, and PSII core proteins D1/D2, HCF136 and HCF173 (PubMed:23027666, PubMed:29438089). Interacts with OHP1 (PubMed:29438089). Forms a trimeric complex with OHP1 and OHP2 that mutually stabilizes each subunit (PubMed:29930106, PubMed:30397023). Predominantly present at thylakoid membranes. Impaired photoautotrophy (PubMed:23027666). Seedling lethal (PubMed:23027666). High chlorophyll fluorescence phenotype and severely affected photosystem II (PSII) subunits accumulation associated with a drastically decreased synthesis of the reaction center protein D1 due to a reduced translation initiation (ribosomal loading) of the corresponding psbA mRNA (PubMed:23027666). Plants lacking both HCF173 and HCF244 display stronger PSII defects (PubMed:23027666). Belongs to the NmrA-type oxidoreductase family.