Structure of a Homodimeric Reaction Center and Insight Into the Evolution of Photosynthesis

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Date/Time
Date(s) - 12 Oct 2017
4:00 PM - 5:00 PM

Location
The Biodesign Institute at ASU


Structure of a Homodimeric Reaction Center

and Insight Into the Evolution of Photosynthesis

 

Structure of a Homodimeric Reaction Center

and Insight Into the Evolution of Photosynthesis

 

 

    Chris Gisriel, Graduate Researcher, School of Molecular Sciences, Arizona State University

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-Å resolution X-ray structure of the homodimeric reaction center from the phototroph Heliobacterium modesticaldum exhibits C2 symmetry about a central axis. The core polypeptide dimer and two small subunits coordinate 54 bacteriochlorophylls 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. The comparison of this structure with those of other reaction centers has allowed us to make hypotheses about how photosynthesis evolved over billions of years.