Centre for Infection, Division of Cellular and Molecular Medicine, St George's University of London, London SW17 0RE, UK.
Mol Microbiol. 2010 Jan;75(1):107-21. doi: 10.1111/j.1365-2958.2009.06957.x. Epub 2009 Nov 10.
Mycobacterium tuberculosis H37Rv contains the kshA (Rv3526) and kshB (Rv3571) genes, encoding 3-ketosteroid 9alpha-hydroxylase (KSH). Consistent with their predicted roles, the DeltakshA and DeltakshB deletion mutants of M. tuberculosis H37Rv were unable to use cholesterol and 4-androstene-3,17-dione as primary carbon and energy sources. Interestingly, DeltakshA and DeltakshB mutants were also unable to metabolize the steroid substrate 5alpha-androstane-3,17-dione, whereas wild-type M. tuberculosis H37Rv could. The deletion of either of these genes lead to rapid death of the microorganism in murine infection models and in macrophages, showing that kshA and kshB are essential factors for M. tuberculosis pathogenesis. Penta-acylated trehalose (PAT) biosynthesis was altered in the DeltakshB mutant, but not the DeltakshA mutant. The DeltakshB mutant synthesizes all other types of lipids. The DeltakshB mutant had a thickened outer layer in its cell wall. KshB thus appears to be involved in multiple processes, probably as a reductase of different oxygenases. We conclude that an impaired 3-ketosteroid 9alpha-hydroxylase activity is the cause of the highly attenuated phenotype of our M. tuberculosis H37Rv mutants.
结核分枝杆菌 H37Rv 含有 kshA（Rv3526）和 kshB（Rv3571）基因，编码 3-酮类固醇 9α-羟化酶（KSH）。与它们的预测作用一致，结核分枝杆菌 H37Rv 的 DeltakshA 和 DeltakshB 缺失突变体无法将胆固醇和 4-雄烯-3,17-二酮用作主要碳和能源来源。有趣的是，DeltakshA 和 DeltakshB 突变体也无法代谢类固醇底物 5α-雄烷-3,17-二酮，而野生型结核分枝杆菌 H37Rv 可以。这些基因中的任何一个缺失都会导致微生物在小鼠感染模型和巨噬细胞中迅速死亡，表明 kshA 和 kshB 是结核分枝杆菌发病机制的必需因素。DeltakshB 突变体中五酰基海藻糖（PAT）的生物合成发生改变，但 DeltakshA 突变体没有。DeltakshB 突变体合成所有其他类型的脂质。DeltakshB 突变体的细胞壁外层变厚。因此，KshB 似乎参与了多个过程，可能作为不同加氧酶的还原酶。我们得出结论，3-酮类固醇 9α-羟化酶活性的降低是我们结核分枝杆菌 H37Rv 突变体高度减毒表型的原因。
