Molecular Basis for the Attachment of S-Layer Proteins to the Cell Wall of Bacillus anthracis,Biochemistry

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Molecular Basis for the Attachment of S-Layer Proteins to the Cell Wall of Bacillus anthracis
Biochemistry ( IF 2.9 ) Pub Date : 2018-03-09 00:00:00 , DOI: 10.1021/acs.biochem.8b00060
David Sychantha ₁ , Robert N. Chapman ₂ , Natalie C. Bamford _{3,

4} , Geert-Jan Boons ₂ , P. Lynne Howell _{3,

4} , Anthony J. Clarke ₁

Affiliation

Bacterial surface (S) layers are paracrystalline arrays of protein assembled on the bacterial cell wall that serve as protective barriers and scaffolds for housekeeping enzymes and virulence factors. The attachment of S-layer proteins to the cell walls of the Bacillus cereus sensu lato, which includes the pathogen Bacillus anthracis, occurs through noncovalent interactions between their S-layer homology domains and secondary cell wall polysaccharides. To promote these interactions, it is presumed that the terminal N-acetylmannosamine (ManNAc) residues of the secondary cell wall polysaccharides must be ketal-pyruvylated. For a few specific S-layer proteins, the O-acetylation of the penultimate N-acetylglucosamine (GlcNAc) is also required. Herein, we present the X-ray crystal structure of the SLH domain of the major surface array protein Sap from B. anthracis in complex with 4,6-O-ketal-pyruvyl-β-ManNAc-(1,4)-β-GlcNAc-(1,6)-α-GlcN. This structure reveals for the first time that the conserved terminal SCWP unit is the direct ligand for the SLH domain. Furthermore, we identify key binding interactions that account for the requirement of 4,6-O-ketal-pyruvyl-ManNAc while revealing the insignificance of the O-acetylation on the GlcNAc residue for recognition by Sap.

中文翻译：

S层蛋白附着在炭疽芽孢杆菌细胞壁上的分子基础

细菌表面（S）层是组装在细菌细胞壁上的蛋白质的多晶阵列，可作为管家酶和毒力因子的保护性屏障和支架。S层蛋白与包括病原体炭疽芽孢杆菌在内的蜡状芽孢杆菌细胞壁的附着是通过其S层同源性域与次级细胞壁多糖之间的非共价相互作用而发生的。为了促进这些相互作用，假定次级细胞壁多糖的末端N-乙酰甘露糖胺（ManNAc）残基必须被缩酮缩丙酮酸化。对于一些特定的S层蛋白，倒数第二个N的O-乙酰化还需要-乙酰氨基葡萄糖（GlcNAc）。在这里，我们提出了炭疽芽孢杆菌的主要表面阵列蛋白Sap的SLH结构域的X射线晶体结构，与4,6- O-缩酮-丙酮基-β-ManNAc-（1,4）-β-复合GlcNAc-（1,6）-α-GlcN。该结构首次揭示了保守的末端SCWP单元是SLH结构域的直接配体。此外，我们发现关键的结合相互作用，解释了4,6- O-缩酮-丙酮基-ManNAc的需求，同时揭示了在Slc识别的GlcNAc残基上O-乙酰化的重要性。

更新日期：2018-03-09

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