The condensing activities of the Mycobacterium tuberculosis type II fatty acid synthase are differentially regulated by phosphorylation
The condensing activities of the Mycobacterium tuberculosis type II fatty acid synthase are differentially regulated by phosphorylation
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DOI：
10.1074/jbc.m601691200
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发表时间：
2006-10-06
影响因子：
4.8
通讯作者：
Kremer, Laurent
中科院分区：
文献类型：
--
作者：
Molle, Virginie;Brown, Alistair K.;Kremer, Laurent
Ser/Thr 蛋白激酶 (STPK) 引起的蛋白质磷酸化最近变得具有重要的生理意义，因为它可能与细菌病原体的毒力有关。尽管结核分枝杆菌有 11 个 STPK，但这些酶底物的性质和功能仍然很大程度上未知。在这项工作中，我们首次鉴定了结核分枝杆菌中的 STPK 底物，形成参与分枝菌酸生物合成的 II 型脂肪酸合酶 (FAS-II) 系统的一部分：丙二酰辅酶 A::AcpM 转酰基酶 mtFabD 和 β-酮脂酰 AcpM 合酶 KasA 和 KasB。所有三种酶在体外均被不同的激酶磷酸化，表明 STPK 与这些底物之间存在复杂的相互作用网络。此外，KasA 和 KasB 在牛分枝杆菌 BCG 中的不同位点均被有效磷酸化，并且可以被结核分枝杆菌 Ser/Thr 磷酸酶 PstP 去磷酸化。酶学研究表明，虽然磷酸化会降低长链脂肪酸合成延伸过程中 KasA 的活性，但这种修饰却增强了 KasB 的活性。磷酸化的这种差异效应可能代表了 FAS-II 系统调节的一种不寻常机制，使病原分枝杆菌能够产生全长分枝杆菌，这是巨噬细胞适应和细胞内生存所必需的。
Phosphorylation of proteins by Ser/Thr protein kinases (STPKs) has recently become of major physiological importance because of its possible involvement in virulence of bacterial pathogens. Although Mycobacterium tuberculosis has eleven STPKs, the nature and function of the substrates of these enzymes remain largely unknown. In this work, we have identified for the first time STPK substrates in M. tuberculosis forming part of the type II fatty acid synthase (FAS-II) system involved in mycolic acid biosynthesis: the malonyl-CoA:: AcpM transacylase mtFabD, and the beta-ketoacyl AcpM synthases KasA and KasB. All three enzymes were phosphorylated in vitro by different kinases, suggesting a complex network of interactions between STPKs and these substrates. In addition, both KasA and KasB were efficiently phosphorylated in M. bovis BCG each at different sites and could be dephosphorylated by the M. tuberculosis Ser/Thr phosphatase PstP. Enzymatic studies revealed that, whereas phosphorylation decreases the activity of KasA in the elongation process of long chain fatty acids synthesis, this modification enhances that of KasB. Such a differential effect of phosphorylation may represent an unusual mechanism of FAS-II system regulation, allowing pathogenic mycobacteria to produce full-length mycolates, which are required for adaptation and intracellular survival in macrophages.