Brown G D, Dave J A, Gey van Pittius N C, Stevens L, Ehlers M R, Beyers A D
Department of Medical Biochemistry/MRC Centre for Molecular and Cellular Biology, University of Stellenbosch, 7505, Tygerberg, South Africa.
Gene. 2000 Aug 22;254(1-2):147-55. doi: 10.1016/s0378-1119(00)00277-8.
There is little information regarding the role of proteolysis in Mycobacterium tuberculosis and no studies on the potential involvement of proteases in the pathogenesis of tuberculosis. We identified five M. tuberculosis genes (mycP1-5) that encode a family of serine proteases (mycosins-1 to 5), ranging from 36 to 47% identity. Each protein contains a catalytic triad (Asp, His, Ser) within highly conserved sequences, typical of proteases of the subtilisin family. These genes are also present in M. bovis BCG and other virulent mycobacteria, but only one homologue (mycP3) was detected in M. smegmatis. The mycosins have N-terminal signal sequences and C-terminal transmembrane anchors, and the localisation of the mycosins to the membrane/cell wall was verified by Western blot analysis of heterologously expressed proteins in cellular fractions of M. smegmatis. In M. tuberculosis, all the mycosins were expressed constitutively during growth in broth. Mycosins-2 and 3 were also expressed constitutively in M. bovis BCG, but no expression of mycosin-1 was detected. Mycosin-2 was modified by cleavage in all three mycobacterial species. The multiplicity and constitutive expression of these proteins suggests that they have an important role in the biology of M. tuberculosis.
关于蛋白水解在结核分枝杆菌中的作用，目前所知甚少，也没有关于蛋白酶可能参与结核病发病机制的研究。我们鉴定出了五个结核分枝杆菌基因（mycP1 - 5），它们编码一个丝氨酸蛋白酶家族（霉菌蛋白酶 - 1至5），序列一致性在36%至47%之间。每个蛋白质在高度保守的序列中都含有一个催化三联体（天冬氨酸、组氨酸、丝氨酸），这是枯草杆菌蛋白酶家族蛋白酶的典型特征。这些基因也存在于牛分枝杆菌卡介苗和其他有毒力的分枝杆菌中，但在耻垢分枝杆菌中仅检测到一个同源物（mycP3）。霉菌蛋白酶具有N端信号序列和C端跨膜锚定序列，通过对耻垢分枝杆菌细胞组分中异源表达蛋白的蛋白质免疫印迹分析，证实了霉菌蛋白酶定位于膜/细胞壁。在结核分枝杆菌中，所有霉菌蛋白酶在肉汤培养生长过程中都是组成性表达的。霉菌蛋白酶 - 2和3在牛分枝杆菌卡介苗中也是组成性表达的，但未检测到霉菌蛋白酶 - 1的表达。在所有三种分枝杆菌中，霉菌蛋白酶 - 2都通过切割进行了修饰。这些蛋白质的多样性和组成性表达表明它们在结核分枝杆菌的生物学特性中具有重要作用。
