BACTERIAL FUNCTION INVOLVED IN CELL GROWTH CONTROL

我们继续研究能量依赖蛋白质 降解在调控基因表达中起重要作用。杆菌作为 模型系统 异常的离子依赖性降解的研究 和天然不稳定的蛋白质已经证明， 因为DnaJ、DnaK和GrpE不是体内降解所必需的 所有Lon底物，但可能有助于促进Lon降解，在一些 通过将底物保持在可溶性形式。 RcsA，a阳性 荚膜基因转录的调节子和Lon底物，需要 DnaJ和DnaK保持活性并可被蛋白酶接近; 依赖于热休克分子伴侣的活动可能提供了基础， 用于胶囊合成的温度调节。 的合成 RcsA在转录水平上通过沉默被调控， 类核相关HNS蛋白。 我们发现了一种小RNA，DsrA， 当其过度产生时，可以抵消HNS沉默rcsA， 其他HNS沉默基因。 在单拷贝中，dsrA对于 胶囊的极低温表达和由dsrB，a 编码小的保守开放阅读框的基因。 我们继续 通过检测Lon，研究Lon底物选择的基础 GST-N融合蛋白和λ N和λ N之间的杂合蛋白的降解 稳定的Nun蛋白 这些结果表明， N和C末端足以识别Lon， 退化，并提供工具，分析的要素， 识别. 对E. 在大肠杆菌中，我们发现了一种新的双组分蛋白酶（ClpQY）， 由热休克hslU hslV操纵子编码，当过量产生时， 降解Lon衬底。 ClpQY和阿尔卑斯山 蛋白酶，一种也能够降解Lon底物的蛋白酶，但仅如此 在E.大肠杆菌，都是一样的。 的 Alp蛋白酶活性的调节显然相当复杂。

We have continued studies on the role that energy-dependent protein degradation plays in regulating gene expression, using E. coli as a model system. Studies on the Lon-dependent degradation of abnormal and naturally unstable proteins has demonstrated that chaperones such as DnaJ, DnaK and GrpE are not necessary for the in vivo degradation of all Lon substrates, but may help promote Lon degradation in some cases by keeping substrates in soluble form. RcsA, a positive regulator of capsule gene transcription and a Lon substrate, requires DnaJ and DnaK to remain active and accessible to the protease; the dependence on heat shock chaperones for activity may provide the basis for the temperature regulation of capsule synthesis. The synthesis of RcsA is regulated at the transcriptional level by silencing by the nucleoid associated HNS protein. We identified a small RNA, DsrA, which, when overproduced, can counteract HNS silencing of rcsA and all other HNS silenced genes. In single copy, dsrA is necessary for the very low temperature expression of capsule and synthesis from dsrB, a gene encoding a small conserved open reading frame. We have continued studies on the basis for Lon substrate selection by examining Lon degradation of GST-N fusions and hybrid proteins between lambda N and the stable Nun protein. These results suggest that regions of both the N and C terminus are sufficient for Lon recognition and degradation, and provide tools for analyzing the elements of recognition. In studies on other energy-dependent proteases in E. coli, we have found that a novel two-component protease (ClpQY) encoded by the heat shock hslU hslV operon can, when overproduced, degrade Lon substrates. It seems possible that ClpQY and the Alp protease, a protease also able to degrade Lon substrates but only thus far detected indirectly in E. coli, are one and the same. The regulation of Alp protease activity is apparently quite complex.