Schaerlaekens K, Schierová M, Lammertyn E, Geukens N, Anné J, Van Mellaert L
Laboratory of Bacteriology, Rega Institute, Katholieke Universiteit Leuven, Minderbroedersstraat 10, B-3000 Leuven, Belgium.
J Bacteriol. 2001 Dec;183(23):6727-32. doi: 10.1128/JB.183.23.6727-6732.2001.
The recently discovered bacterial twin-arginine translocation (Tat) pathway was investigated in Streptomyces lividans, a gram-positive organism with a high secretion capacity. The presence of one tatC and two hcf106 homologs in the S. lividans genome together with the several precursor proteins with a twin-arginine motif in their signal peptide suggested the presence of the twin-arginine translocation pathway in the S. lividans secretome. To demonstrate its functionality, a tatC deletion mutant was constructed. This mutation impaired the translocation of the Streptomyces antibioticus tyrosinase, a protein that forms a complex with its transactivator protein before export. Also the chimeric construct pre-TorA-23K, known to be exclusively secreted via the Tat pathway in Escherichia coli, could be translocated in wild-type S. lividans but not in the tatC mutant. In contrast, the secretion of the Sec-dependent S. lividans subtilisin inhibitor was not affected. This study therefore demonstrates that also in general in Streptomyces spp. the Tat pathway is functional. Moreover, this Tat pathway can translocate folded proteins, and the E. coli TorA signal peptide can direct Tat-dependent transport in S. lividans.
在天蓝色链霉菌（一种具有高分泌能力的革兰氏阳性菌）中，对最近发现的细菌双精氨酸转运（Tat）途径进行了研究。天蓝色链霉菌基因组中存在一个tatC和两个hcf106同源物，同时其信号肽中带有双精氨酸基序的几种前体蛋白表明，天蓝色链霉菌分泌组中存在双精氨酸转运途径。为了证明其功能，构建了一个tatC缺失突变体。该突变损害了抗生链霉菌酪氨酸酶的转运，抗生链霉菌酪氨酸酶是一种在输出前与其反式激活蛋白形成复合物的蛋白质。同样，已知在大肠杆菌中仅通过Tat途径分泌的嵌合构建体pre-TorA-23K，在野生型天蓝色链霉菌中可以转运，但在tatC突变体中则不能。相比之下，依赖Sec的天蓝色链霉菌枯草杆菌蛋白酶抑制剂的分泌不受影响。因此，这项研究表明，在链霉菌属中一般而言，Tat途径也是有功能的。此外，这种Tat途径可以转运折叠的蛋白质，并且大肠杆菌TorA信号肽可以指导天蓝色链霉菌中依赖Tat的转运。
