title: A dimeric mutant of the homotetrameric single-stranded DNA binding protein from Escherichia coli.
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.
authors.affiliation: Biophysical Chemistry, Medical School Hannover, Germany.
authors.forename: Marco
authors.initials: M
authors.lastname: Landwehr
authors.forename: Ute
authors.initials: U
authors.lastname: Curth
authors.forename: Claus
authors.initials: C
authors.lastname: Urbanke
mesh_terms: D019943:Amino Acid Substitution; D001426:Bacterial Proteins / Q000235:genetics / Q000378:metabolism*; D004269:DNA, Bacterial / Q000737:chemistry / Q000235:genetics; D004277:DNA, Single-Stranded / Q000235:genetics / Q000378:metabolism*; D004268:DNA-Binding Proteins / Q000235:genetics / Q000378:metabolism*; D019281:Dimerization; D004926:Escherichia coli / Q000235:genetics / Q000378:metabolism*; D019791:Guanidine / Q000737:chemistry; D008958:Models, Molecular; D008970:Molecular Weight; D016297:Mutagenesis, Site-Directed; D011072:Poly U / Q000378:metabolism; D011487:Protein Conformation; D013050:Spectrometry, Fluorescence; D013329:Structure-Activity Relationship; D014461:Ultracentrifugation
chemical_list: D001426:Bacterial Proteins; D004269:DNA, Bacterial; D004277:DNA, Single-Stranded; D004268:DNA-Binding Proteins; D011072:Poly U; D019791:Guanidine