Ancient archaea provide answers for proteins

Researchers from the University of Cambridge and the University of Technology, Sydney (UTS) are studying the function of a newly discovered family of proteins associated with archaea - microorganisms believed to be amongst the oldest lifeforms on Earth.

Archaea make up the third major grouping of life on the planet, alongside eukaryotes (including all plants and animals) and bacteria. They have existed for 2.5 billion years and play a vital role in recycling the Earth’s elements, yet only now are scientists starting to reveal their secrets.

“Archaea and bacteria joined forces early in evolution, and all other complex life we see around us today is the result,” said Dr Iain Duggin from UTS’s ithree institute, who led the research.

The study focused on a family of proteins called CetZ that act like a miniature skeletal system for archaeal cells, controlling their shape and movement. Scientists had thought this feature only evolved with more complex organisms, but the findings suggest that such behaviour may be an inheritance from archaea.

Writing in the journal Nature, the study authors explained that CetZ is related to proteins in humans and bacteria. They said, “Tubulin is a major component of the eukaryotic cytoskeleton, controlling cell shape, structure and dynamics, whereas its bacterial homologue FtsZ establishes the cytokinetic ring that constricts during cell division … Studying Archaea may provide clues as these organisms share characteristics with Eukarya and Bacteria.”

Dr Duggin collaborated with former colleagues from the MRC Laboratory of Molecular Biology at the University of Cambridge, who conducted protein crystallography. The authors said, “CetZ X-ray crystal structures showed the FtsZ/tubulin superfamily fold, and one crystal form contained sheets of protofilaments, suggesting a structural role.

“Our findings expand the known roles of the FtsZ/tubulin superfamily to include archaeal cell shape dynamics, suggesting that a cytoskeletal role might predate eukaryotic cell evolution, and they support the premise that a major function of the microbial rod shape is to facilitate swimming.”

Tubulin-like proteins in control of cell shape differentiation. Image by Dr Iain Duggin.

Dr Duggin said a better understanding of archaea could have a wide variety of applications - from oil exploration to chemical processing or as a new source of antibiotics - and that the study has helped the researchers understand the differences between their related human and bacterial proteins.

“Whilst tubulin is a key target in cancer drug development, we believe that FtsZ could be an important target for the development of new antibiotics, potentially enabling the design of anti-infective drugs that inhibit bacterial cell division and growth, with fewer side effects,” he said.

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