Verification of a topology model of PorT as an integral outer-membrane protein in Porphyromonas gingivalis.
Verification of a topology model of PorT as an integral outer-membrane protein in Porphyromonas gingivalis.
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DOI：
10.1099/mic.0.024323-0
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发表时间：
2009-02
期刊：
影响因子：
--
通讯作者：
Potempa J
中科院分区：
文献类型：
--
作者：
Nguyen KA;Żylicz J;Szczesny P;Sroka A;Hunter N;Potempa J
PorT是一种膜相关蛋白，对牙周病原体牙龈卟啉单胞菌的一类半胱氨酸蛋白酶（牙龈痛）的成熟和分泌至关重要。先前有报道称PorT位于内膜的质周表面，作为成熟蛋白酶的伴侣。我们的模型表明它是一个完整的外膜蛋白，具有8个反平行的，穿过膜的β-链。在本报告中，外膜定位模型通过PorT对六组氨酸（6×His）标签的结构和功能耐受性得到了证实，这些标签通过位点定向诱变插入到蛋白质的选定位置。有趣的是，影响牙龈蛋白酶分泌的PorT突变增强了PorT基因的表达，同时抑制了牙龈蛋白酶rgpB基因的转录。此外，缺乏牙龈蛋白酶活性的PorT突变体产生了更多的二氨基肽酶和三氨基肽酶活性。在拟杆菌门的限制性成员中发现了PorT同源物，其中PorT有可能参与具有特征c端结构域（CTD）的蛋白质的成熟和分泌。了解PorT的细胞定位将有助于分析该蛋白在出口牙龈痛蛋白和其他ctd类蛋白的新分泌途径中的作用。
PorT is a membrane-associated protein shown to be essential for the maturation and secretion of a class of cysteine proteinases, the gingipains, from the periodontal pathogen Porphyromonas gingivalis. It was previously reported that PorT is located on the periplasmic surface of the inner membrane to function as a chaperone for the maturing proteinases. Our modeling suggested it to be an integral outer membrane protein with eight anti-parallel, membrane-traversing β-strands. In this report, the outer membrane localization model was confirmed by the structural and functional tolerance of PorT to hexa-histidine (6×His) tag insertions at selected locations within the protein using site-directed mutagenesis. Interestingly, those PorT mutations adversely affecting gingipain secretion enhanced expression of the porT gene but at the same time suppressed the transcription of the gingipain rgpB gene. Further, PorT mutants deficient in gingipain activities produced significantly more di- and tri-aminopeptidase activities. PorT homologues have been found in restricted members of the Bacteroidetes phylum where there is potential for PorT to participate in the maturation and secretion of proteins with characteristic C-terminal domains (CTD). Knowledge of the cellular localisation of PorT will enable analysis of the role of this protein in a new secretory pathway for the export of gingipains and other CTD-class proteins.
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影响因子：
3.2
作者：
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