Abstract
BackgroundThermophilic organisms are able to live at high temperatures ranging from 50 to > 100°C. Their proteins must be sufficiently stable to function under these extreme conditions; however, the basis for thermostability remains elusive. Subtle differences between thermophilic and mesophilic molecules can be found when sequences or structures from homologous proteins are compared, but often these differences are family-specific and few general rules have been derived. The availability of complete genome sequences has now made it feasible to perform a large-scale comparison between mesophilic and thermophilic proteins, the latter of which primarily come from archaeal genomes although a few complete genomes of thermophilic eubacteria are also available.ResultsWe compared mesophilic proteins with their thermophilic counterparts of archaeal or eubacterial origins independently. This was based on the assumption that in these two kingdoms, different mechanisms may have been exploited for the adaptation of proteins at high temperatures. We derived the environment specific amino acid compositions of thermophilic proteins from 10 archaeal and seven eubacterial genomes, by aligning a large number of sequences from thermophilic proteins with their close mesophilic homologues of known three-dimensional (3D) structure. We further analysed environment specific substitutions, which lead from mesophilic proteins to either archaeal or eubacterial thermophilic proteins.ConclusionOur comparisons were based on homology-based structural predictions for a large number of thermophilic proteins. We demonstrated that thermal adaptation in the archaeal and eubacterial kingdoms is achieved in different ways. The main differences concern the usage of Gln, Ile and positively charged amino acids. In particular archaeal organisms appeared to have acquired thermostability by substituting non-charged polar amino acids (such as Gln) with Glu and Lys, and non-polar amino acids with Ile on the surface of proteins.
Highlights
Thermophilic organisms are able to live at high temperatures ranging from 50 to > 100°C
GC content does not correlate with optimal growth temperatures (OGTs) and on average, is only slightly higher in eubacteria than in archaea
We show a list of statistically significant cases, in which the likelihood of a substitution leading from a mesophilic protein to a thermophilic archaeal protein or to a thermophilic eubacterial protein is different from the corresponding environment specific amino acid substitution in mesophilic proteins
Summary
Thermophilic organisms are able to live at high temperatures ranging from 50 to > 100°C Their proteins must be sufficiently stable to function under these extreme conditions; the basis for thermostability remains elusive. Many studies have been carried out for several decades, it has so far been difficult to identify any single factor as being primarily responsible for enhancing thermal stability. This is probably because protein stability is determined by a fine balance between several contributing factors. Even considering multiple factors, few general rules have been derived and often rules derived for one protein family did not apply to other families
Sign-in/Register to view highlights & summary Talk to us
Join us for a 30 min session where you can share your feedback and ask us any queries you have
Schedule a callDisclaimer: All third-party content on this website/platform is and will remain the property of their respective owners and is provided on "as is" basis without any warranties, express or implied. Use of third-party content does not indicate any affiliation, sponsorship with or endorsement by them. Any references to third-party content is to identify the corresponding services and shall be considered fair use under The CopyrightLaw.
