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 674s(-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.
