New insights into histidine triad proteins: solution structure of a Streptococcus pneumoniae PhtD domain and zinc transfer to AdcAII.
New insights into histidine triad proteins: solution structure of a Streptococcus pneumoniae PhtD domain and zinc transfer to AdcAII.
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DOI：
10.1371/journal.pone.0081168
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发表时间：
2013
期刊：
影响因子：
3.7
通讯作者：
Durmort C
中科院分区：
文献类型：
--
作者：
Bersch B;Bougault C;Roux L;Favier A;Vernet T;Durmort C
锌（Zn 2+）的稳态对于病原体宿主定殖和入侵至关重要。多组氨酸三联体（Pht）蛋白，位于各种链球菌的表面，已被提出参与锌2+稳态。phtD基因，编码的Zn 2+结合蛋白，被组织在一个操纵子与adcAII编码的胞外部分的Zn 2+转运蛋白。在目前的工作中，我们使用生物化学和结构生物学方法研究PhtD和AdcAII之间的关系。肺炎链球菌（S。pneumoniae）证实了天然PhtD和AdcAII在体内相互作用，证实了我们先前的体外观察结果。NMR用于证明Zn 2+从PhtD（t-PhtD）的137个氨基酸的N-末端结构域的Zn 2+结合形式转移到AdcAII。t-PhtD的高分辨率NMR结构表明，Zn 2+被组氨酸83、86和88以及谷氨酸63结合在四面体位点中。测得的载脂蛋白和锌2 +-t-PhtD的NMR参数的比较表明，锌2+的损失导致在C-末端的螺旋倾向减少，并增加了局部动力学和整体分子体积。与PhtA的55-长片段的晶体结构的结构比较表明，Pht蛋白质由含有保守的HxxHxH基序的三条β-链形成的短重复单元构建。总之，这些结果支持S。pneumoniae PhtD作为Zn2+清除剂用于随后释放至表面转运蛋白AdcAII，导致Zn2+摄取。
Zinc (Zn2+) homeostasis is critical for pathogen host colonization and invasion. Polyhistidine triad (Pht) proteins, located at the surface of various streptococci, have been proposed to be involved in Zn2+ homeostasis. The phtD gene, coding for a Zn2+-binding protein, is organized in an operon with adcAII coding for the extracellular part of a Zn2+ transporter. In the present work, we investigate the relationship between PhtD and AdcAII using biochemical and structural biology approaches. Immuno-precipitation experiments on purified membranes of Streptococcus pneumoniae (S. pneumoniae) demonstrate that native PhtD and AdcAII interact in vivo confirming our previous in vitro observations. NMR was used to demonstrate Zn2+ transfer from the Zn2+-bound form of a 137 amino acid N-terminal domain of PhtD (t-PhtD) to AdcAII. The high resolution NMR structure of t-PhtD shows that Zn2+ is bound in a tetrahedral site by histidines 83, 86, and 88 as well as by glutamate 63. Comparison of the NMR parameters measured for apo- and Zn2+-t-PhtD shows that the loss of Zn2+ leads to a diminished helical propensity at the C-terminus and increases the local dynamics and overall molecular volume. Structural comparison with the crystal structure of a 55-long fragment of PhtA suggests that Pht proteins are built from short repetitive units formed by three β-strands containing the conserved HxxHxH motif. Taken together, these results support a role for S. pneumoniae PhtD as a Zn2+ scavenger for later release to the surface transporter AdcAII, leading to Zn2+ uptake.
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