The reaction center is a membrane-bound complex that mediates the initial photochemical event in the electron transfer process of photosynthesis. Binds 4 bacteriochlorophylls per trimer. Binds 2 bacteriopheophytins per trimer. Binds 1 Fe cation per trimer. Binds 4 Mg(2+) ions per trimer. Binds 1 menaquinone per trimer. Binds 1 ubiquinone per trimer. Heterotrimer composed of subunits L, M, and H. Belongs to the reaction center PuhA family.