A Highly Unusual Thioester Bond in a Pilus Adhesin Is Required for Efficient Host Cell Interaction
A Highly Unusual Thioester Bond in a Pilus Adhesin Is Required for Efficient Host Cell Interaction
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DOI：
10.1074/jbc.m110.149385
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发表时间：
2010-10-29
影响因子：
4.8
通讯作者：
Banfield, Mark J.
中科院分区：
文献类型：
--
作者：
Pointon, Jonathan A.;Smith, Wendy D.;Banfield, Mark J.
许多细菌病原体在称为皮利的长的大分子细丝的尖端呈现粘附素，其通常是重要的毒力决定因子。革兰氏阳性病原体呈递的皮利是如何介导宿主细胞结合的知之甚少。来自重要的人类病原体化脓性链球菌的菌毛粘附素的晶体结构揭示了在半胱氨酸和谷氨酰胺残基的侧链之间形成的内部硫酯键。使用紫外-可见光谱和质谱验证硫酯的存在。这种不寻常的键以前仅在补体和补体样蛋白的硫酯结构域中观察到，其中它用于与靶分子形成共价连接。该结构还揭示了两个分子内异肽键，其中一个通过Lys/Asp残基对形成，其战略定位赋予蛋白质稳定性。通过等位基因置换诱变去除S.化脓性链球菌严重损害细菌对模型宿主细胞的粘附。虽然目前的细菌/宿主细胞相互作用的范例设想强的非共价相互作用，本研究表明，细胞粘附也可能涉及共价键。
Many bacterial pathogens present adhesins at the tips of long macromolecular filaments known as pili that are often important virulence determinants. Very little is known about how pili presented by Gram-positive pathogens mediate host cell binding. The crystal structure of a pilus adhesin from the important human pathogen Streptococcus pyogenes reveals an internal thioester bond formed between the side chains of a cysteine and a glutamine residue. The presence of the thioester was verified using UV-visible spectroscopy and mass spectrometry. This unusual bond has only previously been observed in thioester domains of complement and complement-like proteins where it is used to form covalent attachment to target molecules. The structure also reveals two intramolecular isopeptide bonds, one of these formed through a Lys/Asp residue pair, which are strategically positioned to confer protein stability. Removal of the internal thioester by allele-replacement mutagenesis in S. pyogenes severely compromises bacterial adhesion to model host cells. Although current paradigms of bacterial/host cell interaction envisage strong non-covalent interactions, the present study suggests cell adhesion could also involve covalent bonds.