The Two Variants of the Streptococcus pneumoniae Pilus 1 RrgA Adhesin Retain the Same Function and Elicit Cross-Protection In Vivo
The Two Variants of the Streptococcus pneumoniae Pilus 1 RrgA Adhesin Retain the Same Function and Elicit Cross-Protection In Vivo
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DOI：
10.1128/iai.00601-10
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发表时间：
2010-12-01
影响因子：
3.1
通讯作者：
Masignani, Vega
中科院分区：
文献类型：
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作者：
Moschioni, Monica;Emolo, Carla;Masignani, Vega
30%的肺炎链球菌分离株含有菌毛胰岛1，编码由骨架亚基RrgB和两种辅助蛋白RrgA和RrgC组成的菌毛。RrgA是与菌毛1相关的体外粘附的主要决定因素，在小鼠模型中具有体内保护作用，并且存在于两种变体（进化枝I和II）中。从X射线数据预测的RrgA结构上的序列变异性的映射表明，多样性仅限于蛋白质的“头部”，其中包含推定的结合结构域，而细长的“茎”大多是保守的。为了研究这种变异性是否会影响RrgA的粘附能力，并绘制对结合重要的区域，测试了两种全长蛋白变体和三种重组RrgA部分对肺上皮细胞和纯化的细胞外基质（ECM）组分的粘附。两种RrgA变体显示出相似的结合能力，而没有一种重组片段的粘附水平与全长蛋白质的水平相当，这表明适当的折叠和结构排列对保留蛋白质功能至关重要。此外，在被动免疫的鼠模型中，两种RrgA变体显示出体外交叉反应性和体内交叉保护性。两者合计，这些数据表明，该地区涉及的粘附和功能表位负责的保护能力的RrgA可能是保守的，并在RrgA的“头”域内发现的相当程度的变化可能已产生的免疫压力，而不损害菌毛的功能完整性。
Thirty percent of Streptococcus pneumoniae isolates contain pilus islet 1, coding for a pilus composed of the backbone subunit RrgB and two ancillary proteins, RrgA and RrgC. RrgA is the major determinant of in vitro adhesion associated with pilus 1, is protective in vivo in mouse models, and exists in two variants (clades I and II). Mapping of the sequence variability onto the RrgA structure predicted from X-ray data showed that the diversity was restricted to the "head" of the protein, which contains the putative binding domains, whereas the elongated "stalk" was mostly conserved. To investigate whether this variability could influence the adhesive capacity of RrgA and to map the regions important for binding, two full-length protein variants and three recombinant RrgA portions were tested for adhesion to lung epithelial cells and to purified extracellular matrix (ECM) components. The two RrgA variants displayed similar binding abilities, whereas none of the recombinant fragments adhered at levels comparable to those of the full-length protein, suggesting that proper folding and structural arrangement are crucial to retain protein functionality. Furthermore, the two RrgA variants were shown to be cross-reactive in vitro and cross-protective in vivo in a murine model of passive immunization. Taken together, these data indicate that the region implicated in adhesion and the functional epitopes responsible for the protective ability of RrgA may be conserved and that the considerable level of variation found within the "head" domain of RrgA may have been generated by immunologic pressure without impairing the functional integrity of the pilus.