Analysis of a repeat-containing family of Giardia lamblia variant-specific surface protein genes: diversity through gene duplication and divergence.
Analysis of a repeat-containing family of Giardia lamblia variant-specific surface protein genes: diversity through gene duplication and divergence.
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贾第鞭毛虫变体特异性表面蛋白基因的重复家族分析：通过基因复制和分歧实现多样性。
DOI：
10.1111/j.1550-7408.1995.tb05888.x
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发表时间：
1995
期刊：
影响因子：
--
通讯作者：
Adam,RD
中科院分区：
文献类型：
--
作者：
Yang,YM;Adam,RD
贾第鞭毛虫在其表面表达一组富含半胱氨酸的抗原变异蛋白中的一种，称为变异特异性表面蛋白，由表面标记检测到的大多数蛋白组成。而这些VSP蛋白在宿主对g的免疫应答中可能是重要的免疫优势蛋白。因此，从一种VSP到另一种VSP的表达转换能力可能为滋养体避免宿主免疫反应提供了一种手段。第一个被鉴定的VSP， VSPA6（来自WB分离物的A6克隆，最初称为CRP170），包含18-23个65个氨基酸的重复。我们现在使用重复序列作为探针从WBA6基因组文库中分离出两个与vspA6相关的基因（称为vspA6‐S1， vspA6‐S2）。对vspA6‐S1基因的序列分析显示，该基因的195 bp重复序列有近两个完整的拷贝，编码区5′和3′与重复序列具有大量的核苷酸和翻译氨基酸相似性。vspA6‐S2基因虽然仍然是相关的，但在非重复编码区显示出与vspA6比vspA6‐S1更大的差异，并且包含近4个201 bp重复序列，与195 bp vspA6重复序列相同75%。这些结果表明，基因复制后的分化在vsp基因库的产生中发挥了关键作用。
Giardia lambliatrophozoites express on their surfaces one of a set of cysteine‐rich antigenically variant proteins, called variant‐specific surface proteins, which comprise the majority of proteins detected by surface labeling. While these VSP proteins may be immunodominant proteins important in the host immune response toG. lamblia, the ability to switch expression from one VSP to another may provide a means for the trophozoites to avoid the host immune response. The first VSP characterized, VSPA6 (from the A6 clone of the WB isolate, originally termed CRP170), contains 18–23 copies of a 65 amino acid repeat. We have now used the repeat as a probe to isolate from a WBA6 genomic library two genes related to vspA6 (called vspA6‐S1, vspA6‐S2). Sequence analysis of the vspA6‐S1 gene revealed nearly two complete copies of the 195 bp repeat and substantial nucleotide and translated amino acid similarity in the coding regions 5’and 3’to the repeats. The vspA6‐S2 gene, while still related, showed greater divergence from vspA6 than vspA6‐S1 in the nonrepeat coding region and contained nearly four copies of a 201 bp repeat that was 75% identical to the 195 bp vspA6 repeat. These results suggest that gene duplication followed by divergence has played a key role in the generation of the vsp gene repertoire.