Methylthioinosine Phosphorylase from Pseudomonas aeruginosa. Structure and Annotation of a Novel Enzyme in Quorum Sensing

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• 作者：Rong Guan ; Meng-Chiao Ho ; Steven C. Almo ; Vern L. Schramm
• 刊名：Biochemistry
• 出版年：2011
• 出版时间：February 22, 2011
• 年：2011
• 卷：50
• 期：7
• 页码：1247-1254
• 全文大小：1057K
• 年卷期：v.50,no.7(February 22, 2011)
• ISSN：1520-4995

文摘

The PA3004 gene of Pseudomonas aeruginosa PAO1 was originally annotated as a 5鈥?methylthioadenosine phosphorylase (MTAP). However, the PA3004 encoded protein uses 5鈥?methylthioinosine (MTI) as a preferred substrate and represents the only known example of a specific MTI phosphorylase (MTIP). MTIP does not utilize 5鈥?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 脜 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 鈫?MTI 鈫?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.