Phycobilisomes Supply Excitations to Both Photosystems in a Megacomplex in Cyanobacteria

Abstract

Complexing Photosynthesis Photosynthesis operates through a series of protein complexes that harvest sunlight and turn it into chemical energy. The separate complexes—including photosystems I and II, phycobilisome antennae, and reaction centers—are understood for a number of photosynthetic organisms; however, the large-scale organization and interactions between them are less clear. Using protein cross-linking, Liu et al. (p. 1104 ) demonstrate how the individual components are organized when present as a megacomplex in the cyanobacterium Synechocystis PCC 6803. Time-resolved fluorescence spectroscopy indicated that the phycobilisomes transfer energy to both photosystems, which is consistent with their molecular arrangement.