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Updated: Aug 9, 2026

Iterative Optimization of DNA Duplexes for Crystallization of SeqA-DNA Complexes
Published on: November 1, 2012
A dimeric mutant of the homotetrameric single-stranded DNA binding protein from Escherichia coli
Marco Landwehr1, Ute Curth, Claus Urbanke
1Biophysical Chemistry, Medical School Hannover, Germany.
Abstract:
A single amino acid substitution (Y78R) at the dimer-dimer interface of homotetrameric single stranded DNA binding protein from E. coli (EcoSSB) renders the protein a stable dimer. This dimer can bind single-stranded DNA albeit with greatly reduced affinity. In vivo this dimeric SSB cannot replace homotetrameric EcoSSB. Amino acid changes at the rim of the dimer-dimer interface nearby (Q76K, Q76E) show an electrostatic interaction between a charged amino acid at position 76 and bound nucleic acid. In conclusion, nucleic acid binding to homotetrameric SSB must take place across both dimers to achieve functionally correct binding.
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