The putative propeptide of MycP1 in mycobacterial type VII secretion system does not inhibit protease activity but improves protein stability

查看全文 作　　者：Demeng [1]Sun;Qing [1]Liu;Yao [1]He;Chengliang [1]Wang;Fangming [2]Wu;Changlin [1,2]Tian;Jianye [1]Zang 机构地区：[1]National Laboratory for Physical Science at the Microscale and School of Life Sciences,University of Science and Technology of China,Hefei 230026,China;[2]High Magnetic Field Laboratory,Chinese Academy of Sciences,Hefei 230031,China 出　　处：《Protein & Cell》索引2013年第4卷第12期,共11页 基　　金：This work was supported by funds from the National Basic Research Program(973 Program)(Nos.2011CB911104 and 2012CB917202);the National Natural Science Foundation of China(Grant No.31100538)to F.W.,(Grant No.31170817)to C.T. 摘　　要：Mycosin-1 protease(MycP1)is a serine protease anchored to the inner membrane of Mycobacterium tuberculosis,and is essential in virulence factor secretion through the ESX-1 type VII secretion system(T7SS).Bacterial physiology studies demonstrated that MycP1 plays a dual role in the regulation of ESX-1 secretion and virulence,primarily through cleavage of its secretion substrate EspB.MycP1 contains a putative N-terminal inhibitory propeptide and a catalytic triad of Asp-His-Ser,classic hallmarks of a sub-tilase family serine protease.The MycP1 propeptide was previously reported to be initially inactive and activated after prolonged incubation.In this study,we have deter-mined crystal structures of MycP1 with(MycP124-422)and without(MycP1^(63-422))the propeptide,and conducted EspB cleavage assays using the two proteins.Very high struc-tural similarity was observed in the two crystal structures.Interestingly,protease assays demonstrated positive EspB cleavage for both proteins,indicating that the putative propeptide does not inhibit protease activity.Molecu-lar dynamic simulations showed higher rigidity in regions guarding the entrance to the catalytic site in MycP124-422 than in MycP1^(63-422),suggesting that the putative propeptide might contribute to the conformational stability of the active site cleft and surrounding regions. 关 键 词：type VII ESX-1 secretion system serine protease PROPEPTIDE crystal structure EspB cleavage molecular dynamic simulations