Protein Structures Have Evolved Little in the Last 4 Billion Years, Study Shows

While modern proteins boast a wide range of structural diversity, the nature of how this came to be has long remained a mystery for scientists.

In a new study published in the journal Structure, however, researchers explain how they were able to resurrect 4 billion-year-old Precambrian proteins in the laboratory and, in doing so, gain a first-ever look into protein evolution through an X-ray analysis of their crystal structures.

In doing so, the researchers say they have deciphered little change in the proteins dating back to a time not long after life first originated on Earth and those of the modern world.

"So far, attempts to understand protein structure evolution have been based on the comparison between structures of modern proteins. This is equivalent to trying to understand the evolution of birds by comparing several living birds," senior study author Jose Sanchez-Ruiz of the University of Granada said in a press release. "But it is most useful to study fossils so that changes over evolutionary time are apparent. Our approach comes as close as possible to 'digging up' fossil protein structures."

In a sense, the study is really the culmination of two separate projects.

Previously, Sanzhez-Ruiz constructed a phylogenetic tree of protein sequences through an analysis of the amino acid sequences of the proteins found in organisms from the three domains of life: bacteria, archaea and eukaryotes. In doing so, he and his colleagues were able to essentially resurrect Precambrian proteins and study their features.

Then, in the most recent study, the researchers collaborated with others to analyze the X-ray crystal structures of those proteins he had previously worked so hard to bring back to life.

The similarity they unearthed in the process was one that persisted, it turns out, despite differences in their amino acid sequences.

This discovery, the researchers argue, adds increased support to a model of evolution in which protein structures remain constant over a significant period of time before undergoing changes rather quickly.

Moreover, the study's authors contend both the study and the methods used represent a powerful new approach that could be used to unlock many more insights into the evolution of these structures.

"In addition to uncovering the basic principles of protein structure evolution, our approach will provide invaluable information regarding how the 3D structure of a protein is encoded by its amino acid sequence," Sanchez-Ruiz said. "It could also provide information about how to design proteins with novel structures -- an important goal in protein engineering and biotechnology."