Enzymes that reveal how life began

Researchers from Rutgers University in New Jersey (USA) have discovered the origins of protein structures responsible for metabolism - believed to be the building blocks of life on Earth. 

These protein structures are simple molecules that are understood to have powered early life on Earth. 

The study’s new findings could be used by NASA to help to search for life on other planets in the future. 

The ENIGMA (Evolution of Nanomachines in Geospheres and Microbial Ancestors) research team have predicted what the earliest protein structures looked like 3.5 billion to 2.5 billion years ago.

“We know very little about how life started on our planet. This work allowed us to glimpse deep in time and propose the earliest metabolic proteins,” said co-author Vikas Nanda, a professor of Biochemistry and Molecular Biology at Rutgers.

The research involved scientists retracing the evolution of enzymes (proteins) from the present to the past. They found that there were two missing protein “folds” - that when connected together, revealed the origins of early life.

These two protein “folds” are a ferredoxin fold that binds iron-sulphur compounds, and a “Rossmann” fold, which binds nucleotides (the building blocks of DNA and RNA). These are two pieces of the puzzle that must fit in the evolution of life.

It was by constructing a network of proteins connected by their roles in metabolism, that the team were able to uncover these missing protein pieces. 

Proteins are chains of amino acids that convert nutrients into energy in any living organism. 

These proteins "are the ones that digest food, act as chemical signals in our body, carry haemoglobin and oxygen through our body," explains the researcher leader Hagai Raanan.

There is evidence the two folds may have shared a common ancestor. If this is true, the ancestor may have been the first metabolic enzyme of life.

"We believe we have found the building blocks of life - the Lego assemblage that ultimately led to the evolution of cells, animals and plants”, said Paul G. Falkowski, a senior researcher at ENIGMA.

The research findings are published in the journal Proceedings of the National Academy of Science

Reference: Hagai Raanan el al., “Small protein folds at the root of an ancient metabolic network,” PNAS (2020), www.pnas.org/cgi/doi/10.1073/pnas.1914982117