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Intrinsic basis of thermostability of prolyl oligopeptidase from Pyrococcus furiosus.

ABSTRACT: Salt-bridges play a key role in the thermostability of proteins adapted in stress environments whose intrinsic basis remains to be understood. We find that the higher hydrophilicity of PfP than that of HuP is due to the charged but not the polar residues. The primary role of these residues is to enhance the salt-bridges and their ME. Unlike HuP, PfP has made many changes in its intrinsic property to strengthen the salt-bridge. First, the desolvation energy is reduced by directing the salt-bridge towards the surface. Second, it has made bridge-energy more favorable by recruiting energetically advantageous partners with high helix-propensity among the six possible salt-bridge pairs. Third, ME-residues that perform intricate interactions have increased their energy contribution by making major changes in their binary properties. The use of salt-bridge partners as ME-residues, and ME-residues' overlapping usage, predominant in helices, and energetically favorable substitution are some of the favorable features of PfP compared to HuP. These changes in PfP reduce the unfavorable, increase the favorable ME-energy. Thus, the per salt-bridge stability of PfP is greater than that of HuP. Further, unfavorable target ME-residues can be identified whose mutation can increase the stability of salt-bridge. The study applies to other similar systems.

SUBMITTER: Banerjee S

PROVIDER: S-EPMC8172842 | biostudies-literature |

REPOSITORIES: biostudies-literature

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Project description:Endonuclease Q (EndoQ), a DNA repair endonuclease, was originally identified in the hyperthermophilic euryarchaeon Pyrococcus furiosus in 2015. EndoQ initiates DNA repair by generating a nick on DNA strands containing deaminated bases and an abasic site. Although EndoQ is thought to be important for maintaining genome integrity in certain bacteria and archaea, the underlying mechanism catalyzed by EndoQ remains unclear. Here, we provide insights into the molecular basis of substrate recognition by EndoQ from P. furiosus (PfuEndoQ) using biochemical approaches. Our results of the substrate specificity range and the kinetic properties of PfuEndoQ demonstrate that PfuEndoQ prefers the imide structure in nucleobases along with the discovery of its cleavage activity toward 5,6-dihydrouracil, 5-hydroxyuracil, 5-hydroxycytosine, and uridine in DNA. The combined results for EndoQ substrate binding and cleavage activity analyses indicated that PfuEndoQ flips the target base from the DNA duplex, and the cleavage activity is highly dependent on spontaneous base flipping of the target base. Furthermore, we find that PfuEndoQ has a relatively relaxed substrate specificity; therefore, the role of EndoQ in restriction modification systems was explored. The activity of the EndoQ homolog from Bacillus subtilis was found not to be inhibited by the uracil glycosylase inhibitor from B. subtilis bacteriophage PBS1, whose genome is completely replaced by uracil instead of thymine. Our findings suggest that EndoQ not only has additional functions in DNA repair but also could act as an antiviral enzyme in organisms with EndoQ.IMPORTANCE Endonuclease Q (EndoQ) is a lesion-specific DNA repair enzyme present in certain bacteria and archaea. To date, it remains unclear how EndoQ recognizes damaged bases. Understanding the mechanism of substrate recognition by EndoQ is important to grasp genome maintenance systems in organisms with EndoQ. Here, we find that EndoQ from the euryarchaeon Pyrococcus furiosus recognizes the imide structure in nucleobases by base flipping, and the cleavage activity is enhanced by the base pair instability of the target base, along with the discovery of its cleavage activity toward 5,6-dihydrouracil, 5-hydroxyuracil, 5-hydroxycytosine, and uridine in DNA. Furthermore, a potential role of EndoQ in Bacillus subtilis as an antiviral enzyme by digesting viral genome is demonstrated.

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Intrinsic basis of thermostability of prolyl oligopeptidase from Pyrococcus furiosus.

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