Proteins with CHADs (Conserved Histidine α-Helical Domains) Are Attached to Polyphosphate Granules In Vivo and Constitute a Novel Family of Polyphosphate-Associated Proteins (Phosins)
Proteins with CHADs (Conserved Histidine α-Helical Domains) Are Attached to Polyphosphate Granules In Vivo and Constitute a Novel Family of Polyphosphate-Associated Proteins (Phosins)
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DOI：
10.1128/aem.03399-16
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发表时间：
2017-04-01
影响因子：
4.4
通讯作者：
Jendrossek, Dieter
中科院分区：
文献类型：
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作者：
Tumlirsch, Tony;Jendrossek, Dieter
根据生物信息学证据，我们推测具有CyTH(CyaB硫胺素三磷酸酶)结构域和/或CHAD(保守组氨酸α螺旋结构域)基序的蛋白质可能代表多聚磷酸(PolyP)颗粒相关蛋白。我们没有发现带有CyTH结构域的蛋白质靶向息肉的证据。与此形成对照的是，Ralstonia eutroa H16(A0104和B1017)的两个含有CHAD基序的蛋白与增强型黄色荧光蛋白(EYFP)融合表达，并与息肉颗粒共定位。虽然没有检测到B1017的表达，但通过蛋白质组学分析，在分离的息肉颗粒组分中特异性地鉴定了A0104蛋白。此外，EYFP与灰磁螺菌MGMSRV2-1987的乍得基序蛋白和恶臭假单胞菌的PP2307蛋白的融合也以跨物种特异性的方式与息肉颗粒共定位。这些数据表明，含有乍得的蛋白质通常附着在息肉颗粒上。再加上之前的四种息肉附着蛋白(息肉蛋白)的发现，这项研究的结果将富营养化杆菌中的息肉相关蛋白的数量增加到六种。我们建议将带有乍得基序的息肉颗粒结合蛋白指定为磷酸磷酸，类似于聚羟基烷酸(PHA)积累细菌的聚羟基烷酸(PHA)颗粒表面和油籽植物中的油滴特异性结合的Phasins和Oil osins。重要性从地球上所有物种中普遍存在的息肉可以看出，聚磷酸盐对生命的重要性是显而易见的。在单细胞真核微生物中，息肉位于特定的膜封闭细胞器中，称为酸性钙体。然而，在大多数原核生物中，息肉是以不溶颗粒的形式存在的，以前被指定为伏鲁丁颗粒。关于息肉颗粒的大分子组成几乎一无所知。特别是，息肉颗粒表面是否存在细胞化合物尚未得到研究。在这项研究中，我们鉴定了一类新的附着在息肉颗粒表面的蛋白质，这些蛋白质附着在三个模式物种的甲蛋白细菌、β蛋白细菌和伽马蛋白细菌中。这些蛋白质的特征是存在一个CHAD(保守的组氨酸α螺旋结构域)基序，其功能是息肉颗粒靶向信号。我们建议将含有乍得基序的蛋白质命名为phosins[类似于聚(3-羟基丁酸酯)相关蛋白的phasins和油籽植物中油滴相关蛋白的olosins]。磷酸酶在不同物种中的表达以跨物种特有的方式证实了它们的息肉靶向功能。我们推测，原核生物中的息肉颗粒通常具有复杂的表面结构，由一到几个息肉蛋白和磷酸蛋白组成。我们建议将息肉颗粒与酸性钙体区分开来，将它们命名为多磷脂小体。
On the basis of bioinformatic evidence, we suspected that proteins with a CYTH (CyaB thiamine triphosphatase) domain and/or a CHAD (conserved histidine alpha-helical domain) motif might represent polyphosphate (polyP) granule-associated proteins. We found no evidence of polyP targeting by proteins with CYTH domains. In contrast, two CHAD motif-containing proteins from Ralstonia eutropha H16 (A0104 and B1017) that were expressed as fusions with enhanced yellow fluorescent protein (eYFP) colocalized with polyP granules. While the expression of B1017 was not detectable, the A0104 protein was specifically identified in an isolated polyP granule fraction by proteome analysis. Moreover, eYFP fusions with the CHAD motif-containing proteins MGMSRV2-1987 from Magnetospirillum gryphiswaldense and PP2307 from Pseudomonas putida also colocalized with polyP granules in a transspecies-specific manner. These data indicated that CHAD-containing proteins are generally attached to polyP granules. Together with the findings from four previously polyP-attached proteins (polyP kinases), the results of this study raised the number of polyP-associated proteins in R. eutropha to six. We suggest designating polyP granule-bound proteins with CHAD motifs as phosins (phosphate), analogous to phasins and oleosins that are specifically bound to the surface of polyhydroxyalkanoate (PHA) granules in PHA-accumulating bacteria and to oil droplets in oil seed plants, respectively. IMPORTANCE The importance of polyphosphate (polyP) for life is evident from the ubiquitous presence of polyP in all species on earth. In unicellular eukaryotic microorganisms, polyP is located in specific membrane-enclosed organelles, called acidocalcisomes. However, in most prokaryotes, polyP is present as insoluble granules that have been designated previously as volutin granules. Almost nothing is known regarding the macromolecular composition of polyP granules. Particularly, the absence or presence of cellular compounds on the surface of polyP granules has not yet been investigated. In this study, we identified a novel class of proteins that are attached to the surface of polyP granules in three model species of Alphaproteobacteria, Betaproteobacteria, and Gammaproteobacteria. These proteins are characterized by the presence of a CHAD (conserved histidine alpha-helical domain) motif that functions as a polyP granule-targeting signal. We suggest designating CHAD motifcontaining proteins as phosins [ analogous to phasins for poly(3-hydroxybutyrate) associated proteins and to oleosins for oil droplet-associated proteins in oil seed plants]. The expression of phosins in different species confirmed their polyP-targeting function in a transspecies-specific manner. We postulate that polyP granules in prokaryotic species generally have a complex surface structure that consists of one to several polyP kinases and phosin proteins. We suggest differentiating polyP granules from acidocalcisomes by designating them as polyphosphatosomes.