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A PAS domain within F plasmid TraJ is critical for its function as a transcriptional activator.

机译:F质粒TRAJ内的PAS结构域对于其作为转录激活剂的功能至关重要。

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摘要

TraJ is the positive activator of the major transfer operon in the F plasmid of Escherichia coli that counteracts H-NS silencing at the main transfer promoter (P(Y)). Multiple sequence alignment revealed a putative PAS (Per-ARNT-Sim) domain that might be involved in sensing redox potential or energy levels in the cell. This domain, which contains a conserved PXCXR motif along with a C(X)(9-10)CR/N/K motif of variable position, was identified within the N-terminal region of TraJ orthologues including F TraJ. The 5 cysteine residues in F TraJ were changed to serine to give protein with single or multiple substitutions. Single C to S substitutions had little effect on mating efficiency (ME), whereas cumulative substitutions from the N- to the C-termini (2CS to 5CS) gradually reduced ME to undetectable levels. F TraJ was able to bind to Fe (III) on an affinity sorbent column. This feature was severely impaired for the 5CS mutant. Thus, the cysteine residues within the PAS domain could be the part of a metal-containing redox centre that plays a key role in the transcriptional activation of the P(Y) operon by TraJ.
机译:TRAJ是大肠杆菌的F质粒中的主要转移操纵子的阳性活化剂,其在主要转移启动子处抵消H-NS沉默(P(Y))。多个序列对准揭示了可能涉及感测细胞中的氧化还原电位或能量水平的推定的PAS(每个ARNT-SIM)域。该域,其中包含保守的PXCXR图案以及可变位置的C(x)(9-10)Cr / n / k基序在包括f Traj的Traj Orthologues的N末​​端区域内识别出C(x)(9-10)Cr / n / K基序。将F Traj中的5个半胱氨酸残基改为丝氨酸,以使蛋白质或多种取代。单一C至S替换对交配效率(ME)影响不大,而N-与C-Termini(2CS至5CS)的累积取代逐渐减少了我无法检测到的水平。 F Traj能够在亲和吸附柱上与Fe(III)结合。对于5CS突变体,此功能受到严重受损。因此,PAS结构域内的半胱氨酸残基可以是含金属氧化还原中心的一部分,其在通过Traj的P(Y)操纵子的转录激活中起关键作用。

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