Molle Virginie, Kremer Laurent, Girard-Blanc Christine, Besra Gurdyal S, Cozzone Alain J, Prost Jean-François
Institut de Biologie et Chimie des Protéines, Université de Lyon, Centre National de la Recherche Scientifique, Lyon, France.
Biochemistry. 2003 Dec 30;42(51):15300-9. doi: 10.1021/bi035150b.
In bacteria, regulatory phosphorylation of proteins at serine and/or threonine residues by Ser/Thr protein kinase (STPK) is an emerging theme in prokaryotic signaling, particularly since the prediction of the occurrence of several STPKs from genome sequencing and sequence surveys. Here we show that protein PknH possesses an autokinase activity and belongs to the large STPK family found in Mycobacterium tuberculosis. Evidence is presented that PknH can also phosphorylate EmbR, a protein suspected to modulate the level of arabinosyltransferase activity involved in arabinan biosynthesis of arabinogalactan, a key molecule of the mycobacterial cell wall. Interestingly, EmbR possesses an FHA (forkhead-associated) domain, a newly described phosphoprotein recognition domain, which plays an essential role in PknH-EmbR interaction and phosphorylation of EmbR by PknH. It is demonstrated that mutation of each of three particular residues of this FHA domain, Arg312, Ser326, and Asn348, totally abolishes the PknH-mediated phosphorylation of EmbR, thus highlighting the critical role of this domain in the direct interaction between EmbR and PknH.
在细菌中，丝氨酸/苏氨酸蛋白激酶（STPK）对蛋白质丝氨酸和/或苏氨酸残基的调节性磷酸化是原核生物信号传导中一个新出现的主题，尤其是自从通过基因组测序和序列调查预测出几种STPK的存在以来。在此我们表明，蛋白PknH具有自身激酶活性，属于在结核分枝杆菌中发现的大型STPK家族。有证据表明，PknH还可以磷酸化EmbR，EmbR是一种被怀疑可调节参与阿拉伯半乳聚糖阿拉伯聚糖生物合成的阿拉伯糖基转移酶活性水平的蛋白质，阿拉伯半乳聚糖是分枝杆菌细胞壁的关键分子。有趣的是，EmbR拥有一个FHA（叉头相关）结构域，这是一个新描述的磷蛋白识别结构域，在PknH与EmbR的相互作用以及PknH对EmbR的磷酸化过程中起关键作用。结果表明，该FHA结构域的三个特定残基Arg312、Ser326和Asn348中的每一个发生突变，都会完全消除PknH介导的EmbR磷酸化，从而突出了该结构域在EmbR与PknH直接相互作用中的关键作用。
