A protein, thought to be one of the fundamental building-blocks of life, is not present in certain volcanic single cell organisms. A team of scientists found another in its place. The missing protein, named SSB, performs an essential role binding DNA and protecting it from damage.
The discovery has ramifications for understanding about how life has evolved on earth.The new gene could have applications in biotechnology and the new scientific discipline of synthetic biology.
ssDNA-binding proteins (SSBs) based on the oligonucleotide-binding fold are considered ubiquitous in nature and play a central role in many DNA transactions including replication, recombination, and repair. We demonstrate that the Thermoproteales, a clade of hyperthermophilic Crenarchaea, lack a canonical SSB. Instead, they encode a distinct ssDNA-binding protein that we term “ThermoDBP,” exemplified by the protein Ttx1576 from Thermoproteus tenax.
ThermoDBP binds specifically to ssDNA with low sequence specificity. The crystal structure of Ttx1576 reveals a unique fold and a mechanism for ssDNA binding, consisting of an extended cleft lined with hydrophobic phenylalanine residues and flanked by basic amino acids. Two ssDNA-binding domains are linked by a coiled-coil leucine zipper.
ThermoDBP appears to have displaced the canonical SSB during the diversification of the Thermoproteales, a highly unusual example of the loss of a “ubiquitous” protein during evolution.
The Daily Galaxy via St Andrews University and the Proceedings of the National Academy of Sciences (PNAS)
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