Meidanis Joao, Braga Marilia D V, Verjovski-Almeida Sergio
Instituto de Computação, Universidade de Campinas, Campinas, São Paulo 13083-970, Brazil.
Microbiol Mol Biol Rev. 2002 Jun;66(2):272-99. doi: 10.1128/MMBR.66.2.272-299.2002.
The transport systems of the first completely sequenced genome of a plant parasite, Xylella fastidiosa, were analyzed. In all, 209 proteins were classified here as constitutive members of transport families; thus, we have identified 69 new transporters in addition to the 140 previously annotated. The analysis lead to several hints on potential ways of controlling the disease it causes on citrus trees. An ADP:ATP translocator, previously found in intracellular parasites only, was found in X. fastidiosa. A P-type ATPase is missing-among the 24 completely sequenced eubacteria to date, only three (including X. fastidiosa) do not have a P-type ATPase, and they are all parasites transmitted by insect vectors. An incomplete phosphotransferase system (PTS) was found, without the permease subunits-we conjecture either that they are among the hypothetical proteins or that the PTS plays a solely metabolic regulatory role. We propose that the Ttg2 ABC system might be an import system eventually involved in glutamate import rather than a toluene exporter, as previously annotated. X. fastidiosa exhibits fewer proteins with > or =4 alpha-helical transmembrane spanners than any other completely sequenced prokaryote to date. X. fastidiosa has only 2.7% of all open reading frames identifiable as major transporters, which puts it as the eubacterium having the lowest percentage of open reading frames involved in transport, closer to two archaea, Methanococcus jannaschii (2.4%) and Methanobacterium thermoautotrophicum (2.4%).
对植物寄生细菌——木质部难养菌（Xylella fastidiosa）首个完成全序列测定的基因组的转运系统进行了分析。总共209种蛋白质在此被归类为转运家族的组成成员；因此，除了先前注释的140种转运蛋白外，我们还鉴定出69种新的转运蛋白。该分析为控制其在柑橘树上引发的病害的潜在方法提供了若干线索。在木质部难养菌中发现了一种ADP：ATP转运体，此前仅在细胞内寄生菌中发现过。一种P型ATP酶缺失——在迄今已完成全序列测定的24种真细菌中，只有三种（包括木质部难养菌）没有P型ATP酶，且它们均为昆虫传播的寄生菌。发现了一个不完整的磷酸转移酶系统（PTS），缺少通透酶亚基——我们推测它们要么在假设的蛋白质中，要么PTS仅发挥代谢调节作用。我们提出，Ttg2 ABC系统可能最终是一种参与谷氨酸转运的输入系统，而非如先前注释的甲苯输出系统。与迄今任何其他完成全序列测定的原核生物相比，木质部难养菌中具有≥4个α-螺旋跨膜结构域的蛋白质更少。木质部难养菌所有可鉴定为主要转运蛋白的开放阅读框中，只有2.7%，这使其成为参与转运的开放阅读框比例最低的真细菌，与两种古细菌——詹氏甲烷球菌（2.4%）和嗜热自养甲烷杆菌（2.4%）相近。
