A型鏈球菌serotype M4菌株的轉譯後折疊蛋白PrsA的功能特色

Abstract

PrsA (putative ribose phosphate pyrophosphokinase)與其同源蛋白(PrsA-like protein)可以在許多的革蘭氏陽性菌中被發現，除參與細菌細胞壁與細胞膜蛋白的運輸與折疊，亦參與細菌分泌到外界的分泌蛋白與毒力因子的折疊與穩定。此外PrsA亦調控細菌細胞壁的代謝、細胞泳動力、化學驅動性等的重要生理功能。研究人員發現當剔除金黃色葡萄球菌中的prsA基因後會影響到菌株對壁黴素(teicoplanin)、萬古黴素(vancomycin) 與苯唑西林(oxacillin)三種抗生素的敏感度。 A型鏈球菌(group A Streptococcus) 為一常見的革蘭氏陽性人類病原菌，可造成急性咽喉炎、蜂窩性組織炎、猩紅熱、壞死性筋膜炎、肺部感染、全身性感染、菌血症。因此實驗室建構了剔除PrsA2的突變株(M4△spy1825)，想了解當剔除PrsA後是否會改變A型鏈球菌對抗生素上的敏感度。目前的結果顯示剔除PrsA2並不影響細菌的生長曲線，此外在抗生素的敏感度與殺菌曲線測試中發現突變株(M4Δspy1825)較野生株對達托黴素(daptomycin)、盤尼西林(penicillin)、苯唑西林、萬古黴素、利奈唑胺(linezoid)、鏈黴素(streptomycin)、氧氟沙星(ofloxacin)抗生素敏感度較低不易被殺死。在連續繼代突變測試中發現M4Δspy1825菌株較容易產生最小抑菌濃度的變異，但此變異與細菌本身因自發性突變所產生的抗藥性應無關聯。測試A型鏈球菌野生株與突變株 (M4Δspy1825) 的隔夜培養液發現對於整體的殺菌曲線並無太大的改變。未來將進一步探討A型鏈球菌野生株與突變株(M4Δspy1825)在分泌到環境的蛋白質的種類與產量是否有差異，來了解PrsA2改變對抗生素感受性的原因。

PrsA (putative ribose phosphate pyrophosphokinase) and its homologous protein (PrsA-like protein) can be found in many Gram-positive bacteria. In addition to participate in bacterial cell wall and cell membrane protein transport and folding, it also involves in the maturation and stabilization of varous bacterial secreted protein and virulence factors. PrsA also regulates important physiological functions like bacterial cell wall metabolism, swimming motility and chemotaxis. Researchers had found that removal of the prsA gene in Staphylococcus aureus affects the sensitivity of the strain to the presence of teicoplanin, vancomycin and oxacillin. Group A Streptococcus is a common gram-positive human pathogen that can cause infectious diseases like acute pharyngitis, cellulitis, scarlet fever, necrotizing fasciitis, pulmonary infection, and systemic infection. In order to understand whether PrsA can regulate the antibiotic susceptibility of group A Streptococcus, a deletion mutant lacking the expression of PrsA2 was generated. The results showed that deletion of PrsA2 did not affect the growth curve of group A Streptococcus. In addition, compared with wild-type parental strain, the M4Δspy1825 mutant was less susceptible to various antibiotics, such as daptomycin, penicillin, oxacillin, vancomycin, linezoid, streptomycin, ofloxacin, surviced better in a antibiotic time-kill kinetic assay. M4Δspy1825 mutant rapidly gained the increased minimal inhibitory concentration (MIC) to penicillin and streptomycin in a serial sub-MIC subcultures, which is not relevant to the differed bacterial spontaneous mutation rate. Supplementation with the culture supernatant collected from overnight cultured M4Δspy1825 did not increase the antibiotic resistance of wild-type group A Streptococcus and vice sersa. In the future we will explore the mechanism of PrsA2-mediated change of antibiotic resistance in group A Streptococcus by analysing the species and expression of PrsA2-regulated proteins.