In eukaryotic cells, the N-terminal amino moiety of many proteins is modified by N-acetyltransferases (NATs). This protein modification can alter the folding of the target protein; can affect binding interactions of the target protein with substrates, allosteric effectors, or other proteins; or can trigger protein degradation. In prokaryotes, only ribosomal proteins are known to be N-terminally acetylated, and the acetyltransferases responsible for this modification belong to the Rim family of proteins. Here, we report that, in Salmonella enterica, the sirtuin deacylase CobB long isoform (CobB_L) is N-terminally acetylated by the YiaC protein of this bacterium. Results of in vitro acetylation assays showed that CobB_L was acetylated by YiaC; liquid chromatography-tandem mass spectrometry (LC-MS/MS) was used to confirm these results. Results of in vitro and in vivo experiments showed that CobB_L deacetylase activity was negatively affected when YiaC acetylated its N terminus. We report 1) modulation of a bacterial sirtuin deacylase activity by acetylation, 2) that the Gcn5-related YiaC protein is the acetyltransferase that modifies CobB_L, and 3) that YiaC is an NAT. Based on our data, we propose the name of NatA (N-acyltransferase A) in lieu of YiaC to reflect the function of the enzyme.

在真核细胞中，许多蛋白质的N末端氨基部分被N-乙酰基转移酶（NAT）修饰。这种蛋白质修饰可以改变目标蛋白质的折叠。可以影响靶蛋白与底物，变构效应子或其他蛋白的结合相互作用；或会触发蛋白质降解。在原核生物中，只有核糖体蛋白被N端乙酰化，而负责这种修饰的乙酰基转移酶属于Rim蛋白家族。在这里，我们报告说，在肠沙门氏菌中，瑟土因脱酰基酶CobB长同工型（CobB _L）被该细菌的YiaC蛋白N端乙酰化。体外乙酰化试验的结果表明CobB _L被YiaC乙酰化；液相色谱-串联质谱（LC-MS / MS）用于确认这些结果。体外和体内实验的结果表明，当YaaC乙酰化其N末端时，CobB _L脱乙酰酶活性受到负面影响。我们报告1）通过乙酰化对细菌Sirtuin脱酰基酶活性的调节，2）Gcn5相关的YiaC蛋白是修饰CobB _L的乙酰基转移酶，以及3）YiaC是NAT。根据我们的数据，我们建议使用NatA（N-酰基转移酶A）代替YiaC，以反映该酶的功能。