Purification and composition of photosystem I reaction center of Prochloron sp., an oxygen-evolving prokaryote containing chlorophyll b

AbstractThe photosystem I reaction center complex of the photosynthetic prokaryote Prochloron, present as a symbiont in ascidians from the Red Sea at Eilat (Israel), was isolated and characterized. The complex consists of 4 polypeptide subunits, and therefore is similar to that of cyanophytes and green algae. Their apparent molecular masses (in kDa) are about 70 (subunit I), 16 (subunit II), 10 (subunit III), and 8 (subunit IV). The purified reaction center contains about 40 chlorophyll molecules per P-700 as compared to about 800 in the intact thylakoids. Subunit I has the same apparent electrophoretic mobility and appears as a double polypeptide band as reported for this subunit in higher plants and algae. Immunological cross-reactivity was detected among subunits I and II of Prochloron and photosystem I reaction centers of higher plants and algae