0°C. The DpsSSB and FpsSSB, with Tm of 78.5°C and 69.4°C, demonstrated more thermostablity than the EcoSSB, but still had less thermostable than the TmaSSB, at a Tm 109.3°C [28]. The thermograms of these SSB proteins showed no characteristic signs of heavily aggregated proteins after heat denaturation. Although the proteins under study come from psychrophilic microorganisms, they have a relatively high

thermostability. Figure 7 DSC thermograms of SSB proteins. Samples containing 2 mg/ml of the DpsSSB, ParSSB, PtoSSB, PprSSB, PinSSB, FpsSSB, PcrSSB, EcoSSB, and TmaSSB were analyzed in 50 mM of potassium phosphate buffer pH 7.5 and 150 mM see more NaCl. The melting temperatures are shown. Discussion In this report, we have described the purification and characterization of single-strand DNA-binding proteins from obligate psychrophilic CHIR-99021 manufacturer bacteria D. psychrophila, P. ingrahamii, P. profundum and P. torquis and the facultative psychrophilic bacteria F. psychrophilum, P. arcticus and P. OSI-027 research buy cryohalolentis. All the proteins investigated form tetramers in solution, as demonstrated by three methods: chemical cross-linking experiments,

sedimentation analysis and gel filtration chromatography. The results of the sequence analysis verified that an ssDNA binding domain in one monomer of each protein possesses a canonical oligonucleotide binding fold (OB-fold) very similar to that observed in the structure of the E. coli SSB. The OB-fold in the proteins in question demonstrated a high level of identity and similarity to EcoSSB, with DpsSSB at 55% and 75%, FpsSSB at 38% and 52%, ParSSB at 57% and 73%, PcrSSB at 58% and 74%, PinSSB at 61% and 82%, PprSSB at 82% and 90%, and PtoSSB at 42% and 62%, which was somewhat surprising, given that they come from taxonomical distant microorganisms living in different environments. They show a high differential in both the molecular mass of their monomers and the length

of their amino acid sequences. Of the known SSBs with one OB-fold, the DpsSSB is the smallest and the FpsSSB is the shortest. The ParSSB, PcrSSB, PinSSB, PprSSB and PtoSSB have melting temperatures (Tm) of 59.9°C, 63°C, 57.9°C, Celastrol 59.5°C and 58.7°C, respectively, which are somewhat lower than for the EcoSSB, at 69.0°C. With Tm of 78.5°C and 69.4°C, the DpsSSB and FpsSSB are more thermostable than the EcoSSB, but their thermostability is not at the level of that for the thermophilic TmaSSB, with a Tm 109.3°C, or even for the TaqSSB, with Tm of 86.8°C [28]. The indirect thermal stability tests showed that both mesophilic and psychrophilic SSBs retain their binding activity at temperatures higher than their melting temperature for specified incubation times. These proteins could thus be used in molecular biology in high-temperature reactions such as nucleic acid amplification.