Involved in chloroplast biogenesis. Required for thylakoid membrane development. Seems to be required for plastid-encoded plastid RNA polymerase (PEP)-dependent gene expression. Component of the plastid-encoded plastid RNA polymerase (PEP) complex. Expressed in leaves and flowers. Albino phenotype and seedling lethality under normal growth conditions. Belongs to the MurCDEF family. MurE subfamily.