Structure and flexibility of the thermophilic cold-shock protein of Thermus aquaticus

• We investigated the structure and backbone dynamics of Ta-Csp and Ta-Csp-dT7.
• Ta-Csp has a highly thermostable structure with five salt bridges.
• Conformational exchange occurs only at the β1–β2 surface of dT7 binding site.
• Average conformational exchange rate constant is 674 s−1 for this region.

The thermophilic bacterium Thermus aquaticus is a well-known source of Taq polymerase. Here, we studied the structure and dynamics of the T. aquaticus cold-shock protein (Ta-Csp) to better understand its thermostability using NMR spectroscopy. We found that Ta-Csp has a five-stranded β-barrel structure with five salt bridges which are important for more rigid structure and a higher melting temperature (76 °C) of Ta-Csp compared to mesophilic and psychrophilic Csps. Microsecond to millisecond time scale exchange processes occur only at the β1–β2 surface region of the nucleic acid binding site with an average conformational exchange rate constant of 674 s−1. The results imply that thermophilic Ta-Csp has a more rigid structure and may not need high structural flexibility to accommodate nucleic acids upon cold shock compared to its mesophile and psychrophile counterparts.

Figure optionsDownload as PowerPoint slide