Recombinant Gene Products Group, International Centre for Genetic Engineering and Biotechnology, New Delhi, India.
PLoS One. 2009 Nov 10;4(11):e7615. doi: 10.1371/journal.pone.0007615.
The secretory proteins of Mycobacterium tuberculosis (M. tuberculosis) have been known to be involved in the virulence, pathogenesis as well as proliferation of the pathogen. Among this set, many proteins have been hypothesized to play a critical role at the genesis of the onset of infection, the primary site of which is invariably the human lung.
METHODOLOGY/PRINCIPAL FINDINGS: During our efforts to isolate potential binding partners of key secretory proteins of M. tuberculosis from a human lung protein library, we isolated peptides that strongly bound the virulence determinant protein Esat6. All peptides were less than fifty amino acids in length and the binding was confirmed by in vivo as well as in vitro studies. Curiously, we found all three binders to be unusually rich in phenylalanine, with one of the three peptides a short fragment of the human cytochrome c oxidase-3 (Cox-3). The most accessible of the three binders, named Hcl1, was shown also to bind to the Mycobacterium smegmatis (M. smegmatis) Esat6 homologue. Expression of hcl1 in M. tuberculosis H37Rv led to considerable reduction in growth. Microarray analysis showed that Hcl1 affects a host of key cellular pathways in M. tuberculosis. In a macrophage infection model, the sets expressing hcl1 were shown to clear off M. tuberculosis in much greater numbers than those infected macrophages wherein the M. tuberculosis was not expressing the peptide. Transmission electron microscopy studies of hcl1 expressing M. tuberculosis showed prominent expulsion of cellular material into the matrix, hinting at cell wall damage.
CONCLUSIONS/SIGNIFICANCE: While the debilitating effects of Hcl1 on M. tuberculosis are unrelated and not because of the peptide's binding to Esat6-as the latter is not an essential protein of M. tuberculosis-nonetheless, further studies with this peptide, as well as a closer inspection of the microarray data may shed important light on the suitability of such small phenylalanine-rich peptides as potential drug-like molecules against this pathogen.
结核分枝杆菌（Mycobacterium tuberculosis，M. tuberculosis）的分泌蛋白已被证实与病原体的毒力、发病机制和增殖有关。在这些蛋白中，许多蛋白被假设在感染起始时起着关键作用，而感染的最初部位通常是人体肺部。
方法/主要发现：在从人类肺蛋白文库中分离结核分枝杆菌关键分泌蛋白潜在结合伴侣的过程中，我们分离到了与毒力决定因子蛋白 Esat6 强烈结合的肽段。所有肽段的长度都小于 50 个氨基酸，体内和体外研究均证实了其结合能力。奇怪的是，我们发现这三个结合物都异常富含苯丙氨酸，其中一个结合物是人类细胞色素 c 氧化酶-3（Cox-3）的短片段。三个结合物中最易接近的一个，命名为 Hcl1，也被证明能与分枝杆菌（Mycobacterium smegmatis，M. smegmatis）Esat6 同源物结合。在结核分枝杆菌 H37Rv 中表达 hcl1 会导致其生长显著减少。微阵列分析显示，Hcl1 影响结核分枝杆菌中一系列关键的细胞途径。在巨噬细胞感染模型中，表达 hcl1 的组比未表达肽段的感染巨噬细胞中清除结核分枝杆菌的数量要多得多。对表达 hcl1 的结核分枝杆菌进行透射电子显微镜研究显示，细胞物质明显被排出到基质中，暗示细胞壁受损。
结论/意义：虽然 Hcl1 对结核分枝杆菌的削弱作用与其结合 Esat6 无关，因为后者不是结核分枝杆菌的必需蛋白，但对该肽的进一步研究以及对微阵列数据的更仔细检查可能会揭示这些富含苯丙氨酸的小肽作为针对该病原体的潜在药物样分子的适宜性方面的重要信息。
