Enterococcal cytolysin is a hemolytic virulence factor linked to human disease and increased patient mortality. Produced by pathogenic strains of Enterococcus faecalis, cytolysin is made up of two small, post-translationally modified peptides called CylL_L” and CylL_S”. They exhibit a unique toxicity profile where lytic activity is observed for both mammalian cells and Gram-positive bacteria that is dependent on the presence of both peptides. In this study, we performed alanine substitution of all residues in CylL_L” and CylL_S” and determined the effect on both activities. We identified key residues involved in overall activity and residues that dictate cell type specificity. All (methyl)lanthionines as well as a Gly-rich hinge region were critical for both activities. In addition, we investigated the binding of the two subunits to bacterial cells suggesting that the large subunit CylL_L” has stronger affinity for the membrane or a target molecule therein. Genome mining identified other potential two-component lanthipeptides and provided insights into potential evolutionary origins.

中文翻译：

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肠球菌溶细胞素的构效关系

肠球菌溶细胞素是一种溶血性毒力因子，与人类疾病和患者死亡率增加有关。溶细胞素由粪肠球菌的致病菌株产生，由两个小的翻译后修饰肽组成，称为 CylL _L ” 和 CylL _S ”。它们表现出独特的毒性特征，其中观察到哺乳动物细胞和革兰氏阳性细菌的裂解活性取决于两种肽的存在。在这项研究中，我们对 CylL _L ”和 CylL _{S中的所有残基进行了丙氨酸取代。}”并确定了对这两项活动的影响。我们确定了涉及整体活性的关键残基和决定细胞类型特异性的残基。所有（甲基）羊毛硫氨酸以及富含 Gly 的铰链区对这两项活动都至关重要。此外，我们研究了这两个亚基与细菌细胞的结合，表明大亚基 CylL _L "对膜或其中的靶分子具有更强的亲和力。基因组挖掘确定了其他潜在的双组分羊毛肽，并提供了对潜在进化起源的见解。