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首页> 外文期刊>The FEBS journal >The tryptophan synthase beta-subunit paralogs TrpB1 and TrpB2 in Thermococcus kodakarensis are both involved in tryptophan biosynthesis and indole salvage
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The tryptophan synthase beta-subunit paralogs TrpB1 and TrpB2 in Thermococcus kodakarensis are both involved in tryptophan biosynthesis and indole salvage

机译：色氨酸嗜热球菌中色氨酸合酶β亚基旁系同源蛋白TrpB1和TrpB2均参与色氨酸的生物合成和吲哚的抢救

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摘要

The last two steps of L-tryptophan (Trp) biosynthesis are catalyzed by Trp synthase, a heterotetramer composed of TrpA and TrpB. TrpB catalyzes the condensation of indole, synthesized by TrpA, and serine to Trp. In the hyperthermophilic archaeon Thermococcus kodakarensis, trpA and trpB (trpB1) are located adjacently in the trpCDEGFB1A operon. Interestingly, several organisms possess a second trpB gene (trpB2) encoding TrpB2, located outside of the trp operon in T. kodakarensis. Until now, the physiological function of trpB2 has not been examined genetically. In the present study, we report the biochemical and physiological analyses of TrpB2 from T. kodakarensis. Kinetic analysis indicated that TrpB2 catalyzed the TrpB reaction but did not interact with TrpA as in the case of TrpB1. When growth phenotypes were examined for gene disruption strains, the double-deletion mutant (Delta trpB1 Delta trpB2) displayed Trp auxotrophy, whereas individual single mutants (Delta trpB1 and Delta trpB2 strains) did not. It has been proposed previously that, in Thermotoga maritima, TrpB2 provides an alternate route to generate Trp from serine and free indole (indole salvage). To accurately examine the capacity of TrpB1 and TrpB2 in Trp synthesis via indole salvage, we constructed Delta trpEB1 and Delta trpEB2 strains using strain KUW1 (Delta pyrF Delta trpE) as a host, eliminating the route for endogenous indole synthesis. Indole complemented the Trp auxotrophies of Delta trpEB1 (Delta pyrF Delta trpE Delta trpB1) and Delta trpEB2 (Delta pyrF Delta trpE Delta trpB2) to similar levels. The results indicate that TrpB1 and TrpB2 both contribute to Trp biosynthesis in T. kodakarensis and can utilize free indole, and that indole salvage does not necessarily rely on TrpB2 to a greater extent.
机译：L-色氨酸（Trp）生物合成的最后两个步骤是由Trp合酶催化的，该酶是由TrpA和TrpB组成的异源四聚体。 TrpB催化由TrpA合成的吲哚和丝氨酸与Trp的缩合。在超嗜热古柯氏热球菌中，trpA和trpB（trpB1）相邻位于trpCDEGFB1A操纵子中。有趣的是，几种生物体拥有第二个编码TrpB2的trpB基因（trpB2），位于柯达卡氏菌的trp操纵子之外。到目前为止，尚未对trpB2的生理功能进行遗传学检查。在本研究中，我们报告了来自柯达喀尔血吸虫TrpB2的生化和生理分析。动力学分析表明，TrpB2催化TrpB反应，但不像TrpB1那样与TrpA相互作用。当检查基因突变菌株的生长表型时，双缺失突变体（Delta trpB1 Delta trpB2）显示出Trp营养缺陷型，而单个突变体（Delta trpB1和Delta trpB2菌株）则没有。先前已经提出，在海生热球菌中，TrpB2提供了一种从丝氨酸和游离吲哚（抢救吲哚）产生Trp的替代途径。为了通过吲哚挽救准确检查TrpB1和TrpB2在Trp合成中的能力，我们使用菌株KUW1（Delta pyrF Delta trpE）作为宿主构建了Delta trpEB1和Delta trpEB2菌株，消除了内源吲哚合成的途径。吲哚将Delta trpEB1（Delta pyrF Delta trpE Delta trpB1）和Delta trpEB2（Delta pyrF Delta trpE Delta trpB2）的Trp营养缺陷互补。结果表明，TrpB1和TrpB2都参与了柯达氏球菌的Trp生物合成，并且可以利用游离的吲哚，并且抢救吲哚并不一定在更大程度上依赖于TrpB2。

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