Resolution of the light-harvesting chlorophyll a/b-protein of vicia faba chloroplasts into two different chlorophyll-protein complexes

Abstract

Thylakoids of Vicia faba chloroplasts disaggregated by sodium dodecyl sulfate were separated by means of different electrophoretic systems. Under the conditions of a high resolving gel system the chlorophyll containing zone previously termed chlorophyll-protein complex II or light-harvesting chlorophyll a/b-protein was found to be inhomogeneous. It represents a mixture of two distinct chlorophyll-proteins characterized by different spectral properties and different apoproteins. One chlorophyll-protein exhibits a chlorophyll a/b ratio of 0.9 and is associated with polypetides of 24,000 and 23,000 daltons. The 24,000 dalton band is proved to bind chlorophyll and has a light-harvesting function. The function of the 23,000 dalton band is unknown. The second chlorophyll-protein has a chlorophyll a/b ratio of 2.1 and an additional absorption maximum in the position of 637 nm. It is associated with only one polypeptide which has an apparent molecular weight of 23,000. The two 23,000 dalton polypeptides occurring in both complexes are not identical.