Howard Taylor Ricketts Laboratory, Argonne National Laboratory, Argonne, Illinois, USA.
J Bacteriol. 2013 Mar;195(5):977-89. doi: 10.1128/JB.01274-12. Epub 2012 Dec 14.
The envelope of Bacillus anthracis encompasses a proteinaceous S-layer with two S-layer proteins (Sap and EA1). Protein assembly in the envelope of B. anthracis requires S-layer homology domains (SLH) within S-layer proteins and S-layer-associated proteins (BSLs), which associate with the secondary cell wall polysaccharide (SCWP), an acetylated carbohydrate that is tethered to peptidoglycan. Here, we investigated the contributions of two putative acetyltransferases, PatA1 and PatA2, on SCWP acetylation and S-layer assembly. We show that mutations in patA1 and patA2 affect the chain lengths of B. anthracis vegetative forms and perturb the deposition of the BslO murein hydrolase at cell division septa. The patA1 and patA2 mutants are defective for the assembly of EA1 in the envelope but retain the ability of S-layer formation with Sap. SCWP isolated from the patA1 patA2 mutant lacked acetyl moieties identified in wild-type polysaccharide and failed to associate with the SLH domains of EA1. A model is discussed whereby patA1- and patA2-mediated acetylation of SCWP enables the deposition of EA1 as well as BslO near the septal region of the B. anthracis envelope.
炭疽杆菌的包膜包含一个蛋白 S 层和两种 S 层蛋白（Sap 和 EA1）。B. anthracis 包膜中的蛋白组装需要 S 层蛋白和 S 层相关蛋白（BSLs）中的 S 层同源结构域（SLH），它们与次级细胞壁多糖（SCWP）结合，SCWP 是一种乙酰化的碳水化合物，与肽聚糖相连。在这里，我们研究了两个假定的乙酰转移酶 PatA1 和 PatA2 对 SCWP 乙酰化和 S 层组装的贡献。我们表明，patA1 和 patA2 突变影响炭疽杆菌营养体的链长，并扰乱 BslO 肽聚糖水解酶在细胞分裂隔膜处的沉积。patA1 和 patA2 突变体在包膜中 EA1 的组装中存在缺陷，但仍保留与 Sap 形成 S 层的能力。从 patA1 patA2 突变体中分离出的 SCWP 缺乏在野生型多糖中鉴定出的乙酰部分，并且无法与 EA1 的 SLH 结构域结合。讨论了一种模型，即 patA1 和 patA2 介导的 SCWP 乙酰化使 EA1 以及 BslO 在炭疽杆菌包膜的隔膜区域附近沉积。
