Nanotechnology discovers the construction principles of photosynthesizing proteins

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Scientists at the University of Liverpool have made a breakthrough in the nano-manipulation of bacterial photosynthesizing proteins.

Photosynthesis is one of the most important biological processes, providing energy required for almost all life on Earth. Photosynthesis occurs in specialised biological membranes, called photosynthetic membranes, which accommodate a set of pigment–protein photosynthesizing complexes. These proteins are defined in the photosynthetic membranes, interacting and working with each other to conduct efficient photosynthetic activities.

While we are starting to understand the organisation of protein complexes in the photosynthetic membranes from naturally occurring photoautotrophs, how the photosynthetic protein complexes are constructed and perform efficient electron transfer is not well known.

Using state-of-the-art microscopy known as Atomic Force Microscopy (AFM), researchers have deciphered the nanoscale structure of the photosynthetic membranes that are extracted from a purple photosynthetic bacterium (Blastochloris viridis). Additionally, they applied single-molecule force spectroscopy (SMFS) to “pull” out protein peptides from the photosynthetic complexes in their working conditions. This allowed researchers to monitor the stepwise unfolding process of the structural components of photosynthetic complexes and detect the mechanical forces required in the unfolding process.

This study, published in BBA-Bioenergetics, enhances our understanding of how photosynthetic protein complexes are formed and stabilised in nature to perform photosynthetic electron transduction with a high efficiency.

First author Leanne Miller said: “I was excited to explore the mechanical nature of single proteins, using the biochemistry and nanotechniques developed during my PhD study. These physical features of proteins play important roles in building active complexes in cells.”

“Nature has shown its extremely powerful capacity of designing biological systems with efficiency and adaptation,” said Professor Luning Liu, who led the research from the University’s Institute of Integrative Biology. “Using multidisciplinary techniques, we aim to harness the knowledge learnt from nature to underpin bioengineering of artificial photosynthetic systems and bioenergy production.”

This study also provides a new approach to study the folding and interactions of any proteins with high precision. It could facilitate research in other biological systems.

The research was in collaboration with Dr David Martin from the Department of Physics at the University of Liverpool and the Centre for Cell Imaging (CCI). The project was supported by funding from Royal Society, Biotechnology and Biological Sciences Research Council (BBSRC), and a joint PhD studentship of BBSRC Doctoral Training Partnerships (DTP) and Department of Physics at the University of Liverpool.

Research reference

Leanne C. Miller, Longsheng Zhao, Daniel P. Canniffe, David Martin, Lu-Ning Liu* (2020) Unfolding pathway and intermolecular interactions of the cytochrome subunit in the bacterial photosynthetic reaction center. Biochim Biophys Acta - Bioenergetics, DOI: 10.1016/j.bbabio.2020.148204.

https://www.sciencedirect.com/science/article/pii/S0005272820300542?via%3Dihub