Structure of a bacterial light-harvesting complex

Photosynthetic organisms convert sunlight energy into a form that can be used by cells. Kunio Miki and colleagues have now solved the first near-atomic-level structure of a complete bacterial light-harvesting antenna–reaction centre (LH1–RC) complex, bound to Ca²⁺ and various cofactors. The LH1 subunits form a ring surrounding the reaction centre, with bacteriochlorophyll and spirilloxanthin cofactors positioned within the ring and Ca²⁺ ions on the periplasmic side of LH1. The structure reveals how energy is transferred from the antenna to the reaction centre in a highly efficient way and suggests how ubiquinone might cross a closed LH1 barrier.