中慢生型天山根瘤菌MsiR组成型蛋白突变株的筛选

Screening of MsiR constitutive mutants from Mesorhizobium tianshanense

MsiR蛋白来源于中慢生型天山根瘤菌(Mesorhizobium tianshanense),是Lys R转录调控蛋白家族中的一员,它可以响应宿主植物释放的抗代谢物-刀豆氨酸,激活外运蛋白msiA编码基因的转录表达。通过构建MsiR突变文库,筛选得到了7个MsiR组成型突变蛋白,L166P、A147V、P83L、A278T组成型突变蛋白丧失了对刀豆氨酸的响应,在没有刀豆氨酸时的荧光值为800左右;A147T、E59G组成型突变蛋白仍然可以响应刀豆氨酸的诱导信号,添加刀豆氨酸时荧光值是未添加时的1.7倍。通过蛋白同源建模分析了组成型突变的氨基酸残基在MsiR蛋白上的空间分布及其对MsiR蛋白调控功能可能的影响。组成型突变蛋白的研究对进一步揭示LysR家族蛋白转录调控的机理有重要意义。

MsiR protein, derived from Mesorhizobium tianshanense, is one of LysR-type transcriptional regulators （LTTRs）, which can activate transcription of the ms/A gene in response to anti-metabolite canavanine released by host plant licorice. By building MsiR mutant library, seven MsiR mutants were screened, the mutant protein of L166P, A147V, P83L, A278T lost response to canavanine, and the fluorescence intersity were about 800 without canavanine. While constitutive mutants A147T and E59G can still be induced by canavanine, the fluorescence intonsity of the mutants with eanavanine were 1.7 times of the ones without canavanine. Through the distribution of the mutated amino acid residues in MsiR protein and their possible functions through protein homology modeling, the research for MsiR consititutive mutants may provide inspiration to uncovering regulatory mechanism of LTTRs.