Single Point Mutation and Its Role in Specific Pathogenicity to Reveal the Mechanism of Related Protein Families

Abstract

Postpartum disease of dairy cows caused by persistent bacterial infection is a global disease, which has a serious impact on the development of the dairy industry and brings huge economic losses. As one of the most relevant pathogenic bacteria for postpartum diseases in dairy cows, Trueperella pyogenes can secrete pyolysin (PLO), a member of the cholesterol-dependent cytolysin (CDC) family and recognized as the most important toxin of T. pyogenes .

Revealing the Mechanism of NLRP3 Inflammatory Pathway Activation through K+ Efflux Induced by PLO via Signal Point Mutations

“…During the expression and purification processes, the rPLO mutants were prepared using the same processes as rPLO, and no significant difference in solubility was detected between the mutants and rPLO. By comparing the sequences of the plo gene with other CDC family members, it was found that the sequence identity between the plo gene and other CDC family members was only 31–45%, while the identity between other CDC family members was between 40% and 70% [ 7 ]. Such low sequence identity can also maintain the characteristics of the CDC family in PLO, indicating that the conserved sequences of PLO and other CDC toxins are crucial for PLO to exercise its hemolytic and pore-forming functions.…”

“…Such low sequence identity can also maintain the characteristics of the CDC family in PLO, indicating that the conserved sequences of PLO and other CDC toxins are crucial for PLO to exercise its hemolytic and pore-forming functions. Our previous studies have shown that sites 139 and 240 are highly conserved compared to other pore-forming toxins [ 7 ]. Mutations at conserved sites 139 and 240 can fully demonstrate the functional and structural relationships of PLO.…”

“…Therefore, further research on the pore formation mechanism of these toxins has clinical application value. Our previous data indicated that a single-residue mutation in Asn139Lys in PLO terminated the pore-forming ability of PLO on the cell membrane, while the Phe240Ala mutation only retained a relatively limited pore-forming ability compared to the Asn139Lys mutant, indicating that the 139th residue Asn and 240th residue Phe are crucial for the pore-forming ability of PLO [ 7 ]. Essentially, the overall structure of these mutants remains unchanged compared to the overall structure of PLO monomers.…”

“…PLO is a primary virulence factor of T. pyogenes and capable of lysing immune cells [ 6 ]. PLO is a member of the cholesterol-dependent cytolysin (CDC) family of which the primary structure only presents a low level of homology with other members from 31% to 45% [ 7 ]. Such low homology can still maintain the special structure and function of the CDC family in PLO.…”

“…Some studies have shown that the pathogenicity of purulent T. pyogenes strains using deficient PLO or mutated PLO is reduced compared to strains that produce the same gene toxin in mice [ 3 , 8 ]. Our previous study indicated that intramuscular administration of recombinant PLO (rPLO) protein can upregulate the expression of pro-inflammatory cytokine interleukin-1β (IL-1β) and IL-18 in mice and cause severe tissue damage [ 7 ]. Moreover, we found that PLO is lethal to mice.…”