PMID: 28751471

Authors:

Gisriel C, Sarrou I, Ferlez B, Golbeck JH, Redding KE, Fromme R

Title:

Structure of a symmetric photosynthetic reaction center-photosystem.

Journal:

Science. 2017 Jul 27. pii: eaan5611. doi: 10.1126/science.aan5611.

Abstract:

Reaction centers are pigment-protein complexes that drive photosynthesis by converting light into chemical energy. It is believed that they arose once from a homodimeric protein. The symmetry of a homodimer is broken in heterodimeric reaction center structures, such as those reported previously. The 2.2-A resolution X-ray structure of the homodimeric reaction center/photosystem from the phototroph, Heliobacterium modesticaldum, exhibits perfect C2 symmetry. The core polypeptide dimer and two small subunits coordinate 54 (bacterio)chlorophylls and 2 carotenoids that capture and transfer energy to the electron transfer chain at the center, which performs charge separation and consists of 6 (bacterio)chlorophylls and an iron-sulfur cluster; unlike other reaction centers, it lacks a bound quinone. This structure preserves characteristics of the ancestral reaction center, providing insight into evolution of photosynthesis.