Acidic C-terminal tail of the ssDNA-binding protein of bacteriophage T7 and ssDNA compete for the same binding surface.
ssDNA-binding proteins are key components of the machinery that mediates replication, recombination, and repair. Prokaryotic ssDNA-binding proteins share a conserved DNA-binding fold and an acidic C-terminal tail. It has been proposed that in the absence of ssDNA, the C-terminal tail contacts the ssDNA-binding cleft, therefore predicting that the binding of ssDNA and the C-terminal tail is mutually exclusive. Using chemical cross-linking, competition studies, and NMR chemical-shift mapping, we demonstrate that: (i) the C-terminal peptide of the gene 2.5 protein cross-links to the core of the protein only in the absence of ssDNA, (ii) the cross-linked species fails to bind to ssDNA, and (iii) a C-terminal peptide and ssDNA bind to the same overall surface of the protein. We propose that the protection of the DNA-binding cleft by the electrostatic shield of the C-terminal tail observed in prokaryotic ssDNA-binding proteins, ribosomal proteins, and high-mobility group proteins is an evolutionarily conserved mechanism. This mechanism prevents random binding of charged molecules to the nucleic acid-binding pocket and coordinates nucleic acid-protein and protein-protein interactions.
Marintcheva
Boriana
B
Department of Biological Chemistry and Molecular Pharmacology, Harvard Medical School, Boston, MA 02115, USA.
Marintchev
Assen
A
Wagner
Gerhard
G
Richardson
Charles C
CC
D000143:Acids / Q000737:chemistry*; D000595:Amino Acid Sequence; D017123:Bacteriophage T7 / Q000378:metabolism*; D001665:Binding Sites; D001667:Binding, Competitive; D004277:DNA, Single-Stranded / Q000378:metabolism*; D004268:DNA-Binding Proteins / Q000737:chemistry / Q000378:metabolism*; D008969:Molecular Sequence Data; D019906:Nuclear Magnetic Resonance, Biomolecular; D014764:Viral Proteins / Q000737:chemistry / Q000378:metabolism*
D000143:Acids; D004277:DNA, Single-Stranded; D004268:DNA-Binding Proteins; D014764:Viral Proteins