Displacement of the canonical single-stranded DNA-binding protein in the Thermoproteales
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Single-stranded DNA binding proteins (SSBs) based on the OB-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 protein Ttx1576 from Thermoproteus tenax. ThermoDBP binds specifically to ssDNA with low sequence specificity. The crystal structure of Ttx1576 reveals a unique fold and 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 where a “ubiquitous” protein has been lost in evolution.
Paytubi , S , McMahon , S , Graham , S , Liu , H , Botting , C H , Makarova , K S , Kroonin , E V , Naismith , J & White , M F 2012 , ' Displacement of the canonical single-stranded DNA-binding protein in the Thermoproteales ' , Proceedings of the National Academy of Sciences of the United States of America , vol. 109 , no. 7 , pp. E398-E405 . https://doi.org/10.1073/pnas.1113277108
Proceedings of the National Academy of Sciences of the United States of America
This is the accepted version of this article (c) the authors. The published version is available at DOI: 10.1073/pnas.1113277108
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