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The negative enthalpy change (deltaH(sub obs)) is examined over a much wider temperature range and as a function of monovalent salt concentration and type for SSB binding to (dT)70 under solution conditions that favor the fully wrapped (SSB)65 complex using isothermal titration calorimetry. Over this wider temperature range, a strongly temperature-dependent negative heat capacity change (deltaC(sub p,obs) is observed.

Results show that Escherichia coli homotetrameric SSB protein is transferred from one single-stranded DNA molecule to another with the need for a protein intermediate. Data indicate that the rate of transfer is dependent on the amount of free DNA binding sites within the initital SSB tetramer-single-stranded DNA donor complex.

Research has been conducted on the homotetrameric Escherichia coli SSB protein's binding to the single-stranded oligodeoxynucleotides. The kinetic mechanism of this binding has been investigated under conditions allowing the fully wrapped ssDNA complex formation and the results are reported.

Salt concentration was shown to be significant in the stability and specificity of protein-nucleic acid interactions, as evidenced by the results of binding the tetrameric Escherichia coli single-stranded binding (SSB) protein to the poly(U) nucleic acid. Possible explanation for the event is the role of cations as they are bound to nucleic acids. Equilibrium association constant decreased with increased salt concentrations at all temperatures used when binding SSB proteins with the linear poly(U) nucleic acid.

The equilibrium binding Deinococcus radiodurans single-stranded (ss) DNA binding protein (DrSSB) to ssDNA is examined for comparison with that of Escherichia coli SSB (EcoSSB). The binding enthalpy has shown a large sensitivity to NaCl concentration, similar to that seen for EcoSSB and these common features for SSB proteins having multiple DNA binding domains enable versatility of SSB function in vivo.

Isothermal titration calorimetry was used to probe the specificity and examine the thermodynamics of single-stranded DNA binding protein (SSB) binding to two Escherichia coli proteins important for DNA replication, the x subunit of DNA polymerase III holoenzyme and the PriA helicase. The results suggested that DNA binding proteins could use the interaction of SSB with both x and PriA to gain access to ssDNA by first interacting with the SSB C-termini.

A study shows that Deinococcus radiodurans SSB (DrSSB) facilitates a local denaturation of the DNA helix at the ss-dsDNA junction of partially duplex DNAs with overhangs of both 15 and 30 nucleotides. Results reveal that DrSSb protein can destabilize duplex DNA immediately adjacent to both 3' and 5' ssDNA extensions and may have relevance for a variety of bacterial DNA metabolic processes.

The single-stranded DNA (ssDNA) binding properties of the Saccharomyces cerevisiae replication protein A (scRPA) using fluorescence titrations, isothermal titration calorimetry, and sedimentation equilibrium is examined to determine whether scRPA could bind ssDNA in multiple binding modes. Results reveal that ssRPA could bind to long ssDNA in at least two binding modes in vitro and that the relative stability of these two modes is influenced by the salt concentration.

The Escherichia coli single-stranded DNA binding protein (SSB) plays a central role in DNA metabolism through its high affinity interactions with ssDNA, as well as its interactions with numerous other proteins via its unstructured C-termini. Although SSB interacts with at least 14 other proteins, it is not understood how SSB might recruit one protein over another for a particular metabolic role. To probe the specificity of these interactions, we have used isothermal titration calorimetry to examine the thermodynamics of binding of SSB to two E. coli proteins important for DNA replication, the Χ subunit of DNA polymerase III holoenzyme and the PriA helicase. We find that an SSB tetramer can bind up to four molecules of either protein primarily via interactions with the last ~9 amino acids in the conserved SSB C-terminal tails (SSB-Ct). We observe intrinsic specificity for the binding of an isolated SSB-Ct peptide to PriA over Χ due primarily to a more favorable enthalpic component. PriA and Χ also bind with weaker affinity to SSB (in the absence of ssDNA) than to isolated SSB-Ct peptides, indicating an inhibitory effect of the SSB protein core. Although the binding affinity of SSB for both Χ and PriA is enhanced if SSB is prebound to ssDNA, this effect is larger with PriA indicating a further enhancement of SSB specificity for PriA. These results also suggest that DNA binding proteins such as PriA, which also interact with SSB, could use this interaction to gain access to ssDNA by first interacting with the SSB C-termini. [ABSTRACT FROM AUTHOR]