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Acidic C-Terminal Tail of the ssDNA-Binding Protein of Bacteriophage T7 and ssDNA Compete for the Same Binding Surface
Boriana Marintcheva, Assen Marintchev, Gerhard Wagner and Charles C. Richardson
Proceedings of the National Academy of Sciences of the United States of America
Vol. 105, No. 6 (Feb. 12, 2008), pp. 1855-1860
Published by: National Academy of Sciences
Stable URL: http://www.jstor.org/stable/25451378
Page Count: 6
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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.
Proceedings of the National Academy of Sciences of the United States of America © 2008 National Academy of Sciences