Laboratoire de Chimie Bactérienne, FR 3479, CNRS, Aix-Marseille Université, 13402 Marseille Cedex 20, France.
J Biol Chem. 2012 Jun 15;287(25):20830-8. doi: 10.1074/jbc.M112.340331. Epub 2012 Apr 27.
In Bacillus subtilis, the ribosome-associated GTPase CpgA is crucial for growth and proper morphology and was shown to be phosphorylated in vitro by the Ser/Thr protein kinase PrkC. To further understand the function of the Escherichia coli RsgA ortholog, CpgA, we first demonstrated that its GTPase activity is stimulated by its association with the 30 S ribosomal subunit. Then the role of CpgA phosphorylation was analyzed. A single phosphorylated residue, threonine 166, was identified by mass spectrometry. Phosphoablative replacement of this residue in CpgA induces a decrease of both its affinity for the 30 S ribosomal subunit and its GTPase activity, whereas a phosphomimetic replacement has opposite effects. Furthermore, cells expressing a nonphosphorylatable CpgA protein present the morphological and growth defects similar to those of a cpgA-deleted strain. Altogether, our results suggest that CpgA phosphorylation on Thr-166 could modulate its ribosome-induced GTPase activity. Given the role of PrkC in B. subtilis spore germination, we propose that CpgA phosphorylation is a key regulatory process that is essential for B. subtilis development.
在枯草芽孢杆菌中，与核糖体相关的 GTP 酶 CpgA 对生长和适当的形态至关重要，并且已经证明其在体外可被丝氨酸/苏氨酸蛋白激酶 PrkC 磷酸化。为了进一步了解大肠杆菌 RsgA 同源物 CpgA 的功能，我们首先证明其 GTP 酶活性与其与 30S 核糖体亚基的结合有关。然后分析了 CpgA 磷酸化的作用。通过质谱鉴定了一个单一的磷酸化残基，即苏氨酸 166。CpgA 中该残基的磷酸化缺失会导致其与 30S 核糖体亚基的亲和力和 GTP 酶活性降低，而磷酸模拟取代则具有相反的效果。此外，表达不可磷酸化 CpgA 蛋白的细胞表现出与 cpgA 缺失菌株相似的形态和生长缺陷。总之，我们的结果表明，CpgA 上 Thr-166 的磷酸化可以调节其受核糖体诱导的 GTP 酶活性。鉴于 PrkC 在枯草芽孢杆菌孢子萌发中的作用，我们提出 CpgA 磷酸化是一个关键的调节过程，对枯草芽孢杆菌的发育至关重要。
