Sequence Logos Derived from HVRs in M Proteins

The sequence logo in Figure 5A was derived from seven HVRs known to bind C4BP (Figure 1B). To analyze additional C4BP-binding HVRs, we compared the HVRs in M proteins of all OF+ strains studied here. Although molecular analysis has not conclusively shown that these HVRs bind C4BP, it seems likely that they do because all OF+ strains bind C4BP (Figure 2, upper panel), and because the ability to bind C4BP has been attributed to the M protein HVR in all OF+ strains analyzed [18,25] (this paper). To analyze non�CC4BP-binding HVRs, we used data for the 11 nonbinding strains included in Figure 2, lower panel. (A) Logo derived from the HVRs in 47 M proteins expressed by OF+ C4BP-binding strains of different serotype (i.e., all strains in upper panel of Figure 2). This logo is similar to that derived from known C4BP-binding HVRs (Figure 5A). In particular, the C-terminal half is less variable than the N-terminal half and includes two dominating Leu residues and a preponderance of negatively charged residues. (B) Logo derived from 11 non�CC4BP-binding HVRs. The appearance of this logo is different from that of the logos in Figures 5A and (A). Although dominating Leu residues are seen also in this logo (most likely reflecting a coiled-coil structure), the variability is similar in both halves of the logo, and it is not clear that the C-terminal half contains a preponderance of negatively charged residues. The logos must be compared with caution, but this analysis suggests that the distribution of residues is different for those HVRs that bind C4BP and those that do not. To construct these logos, residues 1�C50 of the indicated HVRs were aligned using ClustalW. The two most conserved Leu residues were used to manually align these HVRs to those analyzed in Figure 5A. Note that the logos shown here only include the 39 residues predicted to correspond to the C4BP-binding region analyzed in Figure 5A. (303 KB PDF)

图5A中的序列标识图源自7个已知可结合补体C4结合蛋白（C4BP）的高变区（hypervariable region，HVR）[参见图1B]。为分析更多可结合C4BP的HVR，我们对本研究中所有OF+菌株的M蛋白高变区进行了比对。尽管目前尚未通过分子实验确凿证实这些HVR可结合C4BP，但结合以下两点推测其大概率具备该结合能力：其一，所有OF+菌株均能结合C4BP（参见图2上半部分）；其二，已有研究[18,25]及本研究均表明，所有被分析的OF+菌株中，M蛋白的HVR是其结合C4BP的关键区域。

为分析非C4BP结合型HVR，我们采用了图2下半部分所包含的11株非结合菌株的相关数据。（A）本标识图源自47株不同血清型OF+ C4BP结合型菌株所表达的M蛋白HVR（即图2上半部分的全部菌株）。该标识图与已知C4BP结合型HVR的标识图（图5A）高度相似：具体而言，其C端半区的变异度低于N端半区，且包含两个优势亮氨酸残基与大量带负电荷的氨基酸残基。
（B）本标识图源自11株非C4BP结合型菌株的HVR。该标识图的外观与图5A及（A）中的标识图存在显著差异：尽管此标识图中同样存在优势亮氨酸残基（这大概率对应卷曲螺旋结构），但其两个半区的变异度相近，且未观察到C端半区富集带负电荷氨基酸残基的特征。尽管需谨慎比对不同标识图，但本分析结果表明，可结合C4BP的HVR与非结合型HVR的氨基酸残基分布存在差异。

为构建上述标识图，我们使用ClustalW对目标HVR的1~50位氨基酸残基进行了多序列比对，并以两个最保守的亮氨酸残基作为手动比对锚点，将这些HVR与图5A中分析的HVR进行对齐。需注意：本研究展示的标识图仅包含对应图5A中分析的C4BP结合区域的39个预测氨基酸残基。（303 KB PDF）