Isolation and characterization of light harvesting bacteriochlorophyll · protein complexes from Rhodopseudomonas capsulata

Abstract

The isolation of two native light harvesting bacteriochlorophyl · protein complexes from Rhodopseudomonas capsulata is described. The light harvesting bacteriochlorophyll I (B 875) has been isolated from the blue-green mutant Ala + lacking both carotenoids and light harvesting bacteriochlorophyll II. Light harvesting bacteriochlorophyll I is associated with a protein (light harvesting band 2) of 12 000 molecular weight. Light harvesting bacteriochlorophyll II complex has been isolated from the mutant Y5 lacking a reaction center and light harvesting bacteriochlorophyll I. Light harvesting bacteriochlorphyll II (B 800 + 850) together with carotenoids is associated with two polypeptides (light harvesting bands 3 and 4) having molecular weights of about 8000 and 10 000 (sodium dodecyl sulfate polyacrylamide gel electrophoresis). A third protein (light harvesting band 1) is in the purified light harvesting II fraction (mol. wt. approx. 14 000), but not associated with bacteriochlorophyll or carotenoids. The amino acid composition of the 3 antenna pigment II proteins is given. The polarity of these proteins was found to be 48%. From the amino acid composition the following molecular weights were calculated band 1: 17 350, band 3: 13 350 and band 4: 10 500.