Photosynthesis is one of the most important biological processes in the
world. It works by using photosynthetic reaction centers (RC) - specialized
membrane proteins - which collect the energy from light and use it to pump
electrons across a biological membrane from one cellular electron carrier to
another, resulting in the conversion of electromagnetic into chemical
energy, which can be used by organisms.
A team of scientists from Arizona State University (ASU) and Pennsylvania
State University has taken a step closer to unlocking the secrets of
photosynthesis. The research team believes that the first reaction center
was simpler than the versions available today. In terms of the protein
structure, it was a homodimer - that is, two copies of the same polypeptide
came together to form a symmetric structure. The reaction centers whose
structures we know are all heterodimers in which this inherent symmetry has
been broken, although at their heart they still retain the vestiges of the
original symmetric architecture.
The research showed the first homodimeric RC structure and it sheds light in
several ways on what the ancestral RC may have looked like. The overall
architecture of the protein is very similar to photosystems of plants and
cyanobacteria and the RC of the purple sulfur bacteria.