Displacement of the canonical single-stranded DNA-binding protein in the Thermoproteales

Sonia Paytubi, Stephen McMahon, Shirley Graham, Huanting Liu, Catherine Helen Botting, Kira S. Makarova, Eugene V. Kroonin, Jim Naismith, Malcolm F White

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29 Citations (Scopus)
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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.
Original languageEnglish
Pages (from-to)E398-E405
Number of pages8
JournalProceedings of the National Academy of Sciences of the United States of America
Issue number7
Early online date21 Nov 2011
Publication statusPublished - 14 Feb 2012


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  • BBSRC BBS/B/14426: SPORT

    Naismith, J.



    Project: Standard

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