In Brucella spp., the type IV secretion system (T4SS) is essential for bacterial intracellular survival and inhibition of the host innate immune response. The Brucella T4SS secretes 15 different effectors to escape host immunity and promote intracellular replication. Among them, BspF has a GNAT-family acetyltransferase domain, implying its acetyltransferase activity. We confirmed that BspF has acetyltransferase activity (data not shown) and de-crotonyltransferase activity. However, BspF overexpressed in HEK-293T cells can also enhance octamer crotonylation in vitro. Then we enriched crotonylated proteins and conducted LC-MS to study the crotonylation changes of proteins in HEK-293T cells caused by BspF overexpression. A total of 5,559 crotonylation sites were identified on 1,525 different proteins, of which 331 sites on 265 proteins were significantly changed. We found that Rab9A and RAP1B in proteomics data have a great impact on Brucella survival, so we speculate that BspF may influence the function of host proteins by altering crotonylation, thereby promoting the intracellular propagation of Brucella.

在 布鲁氏菌spp.，IV 型分泌系统 (T4SS) 对细菌细胞内存活和抑制宿主先天免疫反应至关重要。这布鲁氏菌T4SS 分泌 15 种不同的效应物来逃避宿主免疫并促进细胞内复制。其中，BspF 具有 GNAT 家族乙酰转移酶结构域，表明其具有乙酰转移酶活性。我们证实 BspF 具有乙酰转移酶活性（数据未显示）和去巴豆酰转移酶活性。然而，在 HEK-293T 细胞中过表达的 BspF 也可以增强八聚体巴豆酰化体外. 然后我们富集巴豆酰化的蛋白质并进行LC-MS研究BspF过表达引起的HEK-293T细胞中蛋白质的巴豆酰化变化。在 1,525 种不同的蛋白质上共鉴定了 5,559 个巴豆酰化位点，其中 265 种蛋白质上的 331 个位点发生了显着变化。我们发现蛋白质组学数据中的 Rab9A 和 RAP1B 对布鲁氏菌 因此我们推测 BspF 可能通过改变巴豆酰化来影响宿主蛋白的功能，从而促进 布鲁氏菌.