Stability of the Thermus thermophilus outer membrane protein TtoA against heat and denaturants

Abstract

TtoA is a major outer membrane protein (Omp) with β-barrel structure from the thermophilic eubacterium T. thermophilus. FT-IR spectroscopy and SDS PAGE analysis were used to monitor the stability of detergent-solubilised TtoA under denaturing conditions. Heat as well as the common denaturants urea and SDS were applied to affect the TtoA structure. The protein has proven to be extremely thermostable in its native form. Denaturants likewise only have little effects on the protein's structure. In detail, a SDS concentration of 1% as is typical for Laemmli buffer does not have an impact on the structure of TtoA, even in combination with a temperature of 99°C. The same holds true for urea concentrations below 8 M. Only the combination of highly concentrated urea or SDS in combination with incubating the protein at 99°C for 10 minutes leads to a change of the secondary structure in TtoA.