Methylthioinosine Phosphorylase from Pseudomonas aeruginosa. Structure and Annotation of a Novel Enzyme in Quorum Sensing
Methylthioinosine Phosphorylase from Pseudomonas aeruginosa. Structure and Annotation of a Novel Enzyme in Quorum Sensing
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DOI：
10.1021/bi101642d
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发表时间：
2011-02-22
期刊：
影响因子：
2.9
通讯作者：
Schramm, Vern L.
中科院分区：
文献类型：
--
作者：
Guan, Rong;Ho, Meng-Chiao;Schramm, Vern L.
铜绿假单胞菌PAO1的PA3004基因最初被注释为5‘-甲硫腺苷磷酸化酶(MTAP)。然而，PA3004编码的蛋白质使用5‘-甲基硫代肌苷(MTI)作为首选底物，并且代表了唯一已知的特定MTI磷酸化酶(M TIP)的例子。MTIP不利用5‘-甲硫腺苷(MTA)。肌苷是一种弱底物，其k(CAT)/K-m值是MTI的290倍，是第二好的底物。铜绿假单胞菌MTIP(PaMTIP)与次黄嘌呤形成的络合物的晶体结构为2.8埃分辨，显示出三重对称的同源三聚体。PaMTIP的甲硫代核糖结合区和磷酸结合区与MTAP相似，嘌呤结合区与嘌呤核苷磷酸化酶(PNPs)相似。MTA在铜绿假单胞菌中的分解代谢包括脱氨为MTI和磷酸化为次黄嘌呤(MTA->；MTI->；次黄嘌呤)。这一途径也存在于恶性疟原虫中，其中嘌呤核苷磷酸化酶(PfPNP)同时作用于肌苷和MTI。鉴定了三个紧结合的PAMTIP过渡态类似物，其离解常数在皮摩尔范围内。抑制剂的特异性提示PAMTIP的早期解离过渡状态。群体感应分子与细菌病原体中MTA的代谢有关，提示PaMTIP是一个潜在的治疗靶点。
The PA3004 gene of Pseudomonas aeruginosa PAO1 was originally annotated as a 5'-methylthioadenosine phosphorylase (MTAP). However, the PA3004 encoded protein uses 5'-methylthioinosine (MTI) as a preferred substrate and represents the only known example of a specific MTI phosphorylase (M TIP). MTIP does not utilize 5'-methylthioadenosine (MTA). Inosine is a weak substrate with a k(cat)/K-m value 290-fold less than MTI and is the second best substrate identified. The crystal structure of P. aeruginosa MTIP (PaMTIP) in complex with hypoxanthine was determined to 2.8 angstrom resolution and revealed a 3-fold symmetric homotrimer. The methylthioribose and phosphate binding regions of PaMTIP are similar to MTAPs, and the purine binding region is similar to that of purine nucleoside phosphorylases (PNPs). The catabolism of MTA in P. aeruginosa involves deamination to MTI and phosphorolysis to hypoxanthine (MTA -> MTI -> hypoxanthine). This pathway also exists in Plasmodium falciparum, where the purine nucleoside phosphorylase (PfPNP) acts on both inosine and MTI. Three tight-binding transition state analogue inhibitors of PaMTIP are identified with dissociation constants in the picomolar range. Inhibitor specificity suggests an early dissociative transition state for PaMTIP. Quorum sensing molecules are associated with MTA metabolism in bacterial pathogens suggesting PaMTIP as a potential therapeutic target.