June 2021
Vol 7, Issue 25

About The Cover

Cover image expansion

ONLINE COVER The reaction center (RC)—light-harvesting complex 1 (LH1) supercomplex is a membrane pigment-protein complex that plays an essential role in bacterial photosynthesis. LH1 captures energy from the Sun and rapidly sends it to the RC, which initiates change separation and electron transfer. While RC-LH1 structures have previously been resolved, there have not been any high-resolution structures of complexes that include PufX, a protein found in all Rhodobacter species that is important for bacterial growth and the photosynthetic process. To address long-standing questions about how PufX is integrated into the RC-LH1 supercomplex and how it contributes to photosynthesis, Bracun et al. developed the first high-resolution structure of a PufX-containing photosynthetic complex—a 2.8 Å cryo-EM structure of the RC–LH1—PufX supercomplex from the bacteria Rhodobacter veldkampii. The researchers observed that PufX acts as a molecular "cross brace," reinforcing the RC-LH1 structure by forming extensive networks with proteins of the RC, LH1, and pigments. They also found that PufX also provides an opening in the LH1 architecture that allows specific channels for quinone/quinol exchange, an important contribution to bacterial photosynthesis. [CREDIT: LUNING LIU]