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首页> 外文期刊>Proceedings of the National Academy of Sciences of the United States of America >Substrate sequestration by a proteolrtically inactive Lon mutant
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Substrate sequestration by a proteolrtically inactive Lon mutant

机译：蛋白质惰性的Lon突变体隔离底物

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Lon protein of Escherichia coli is an ATP- dependent protease responsible for the rapid turnover of both abnormal and naturally unstable proteins, including SulA, a cell division inhibitor made after DNA damage, and RcsA, a positive regulator of transcription. Lon is a multimer of identical 94-kDa subunits, each containing a consensus ATP- ase motif and a serine active site. We found that overexpress- ing Lon, which is mutated for the serine active site (LonS679A) and is therefore devoid of proteolytic activity, unexpectedly led to complementation of the UV sensitivity and capsule overproduction of a ion deletion mutant. SulA was not degraded by LonS679A, but rather was completely protected by the Lon mutant from degradation by other cellular pro- teases. We interpret these results to mean that the mutant LonS679A binds but does not degrade Lon substrates, result- ing in sequestration of the substrate proteins and interference with their activities, resulting in apparent complementation. Lon that carried a mutation in the consensns ATPase site, either with or without the active site serine, was no longer able to complement a #delta#lon mutant. These in vivo results suggest that the pathway of degradation by Lon couples ATP- dependent unfolding with movement of the substrate into protected chambers within Lon, where it is held until degra- dation proceeds. In the absence of degradation the substrate remains sequestered. Comparison of our results with those from a number of other systems suggest that proteins related to the regulatory portions of energy-dependent proteases a
机译：大肠杆菌的Lon蛋白是一种ATP依赖性蛋白酶，负责异常和天然不稳定蛋白的快速更新，包括SulA（一种在DNA损伤后产生的细胞分裂抑制剂）和RcsA（一种转录的阳性调节剂）。 Lon是相同的94-kDa亚基的多聚体，每个亚基包含共有的ATP酶基序和丝氨酸活性位点。我们发现过表达的Lon突变为丝氨酸活性位点（LonS679A），因此缺乏蛋白水解活性，出乎意料地导致了UV敏感性的互补和离子缺失突变体的胶囊过量生产。 SulA不会被LonS679A降解，而是被Lon突变体完全保护免受其他细胞蛋白酶的降解。我们将这些结果解释为意味着突变体LonS679A结合但不降解Lon底物，导致隔离底物蛋白并干扰其活性，从而导致明显的互补。在共有ATPase位点中突变的Lon，无论有无活性位点丝氨酸，都不再能够与#deltalon突变体互补。这些体内结果表明，Lon的降解途径将ATP依赖的解偶联与底物移动到Lon内受保护的腔室中的过程相结合，直到发生降解为止。在没有降解的情况下，底物保持隔离状态。将我们的结果与其他系统的结果进行比较，结果表明与能量依赖性蛋白酶的调节部分相关的蛋白质

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