Wöhrl B M, Wehmeier U F, Lengeler J W
Max-Planck-Institut für Molekulare Genetik, Abteilung Schuster, Berlin, Federal Republic of Germany.
Mol Gen Genet. 1990 Nov;224(2):193-200. doi: 10.1007/BF00271552.
In Klebsiella pneumoniae the gene products involved in the degradation of the ketose L-sorbose are encoded in the sor operon. It comprises, besides structural genes for uptake and catabolism, a promoter-proximal gene sorC, encoding a protein SorC of Mr 40 kDa, for which no enzymatic function has been detected. All sor genes are coordinately expressed and inducible by L-sorbose. Polar insertions and frameshift mutations in sorC cause a pleiotropic negative effect on the expression of all other sor genes. This defect is complemented in trans by the wild-type sorC+ allele for frameshift mutations, but not for polar insertions. A single promoter for all sor genes, for which SorC is the activator, thus seems to be located in front of sorC. The repressor activity of SorC was demonstrated by complementation of constitutive sorC alleles with a sorC+ allele leading to inducible expression of all sor genes, including sorC, which, as visualized by the use of a series of lacZ fusions, thus autoregulates its expression, both as an activator and a repressor.
在肺炎克雷伯菌中，参与酮糖L-山梨糖降解的基因产物由sor操纵子编码。除了参与摄取和分解代谢的结构基因外，它还包含一个启动子近端基因sorC，编码一种40 kDa的蛋白质SorC，尚未检测到其酶促功能。所有sor基因都是协调表达的，并且可被L-山梨糖诱导。sorC中的极性插入和移码突变对所有其他sor基因的表达产生多效性负面影响。对于移码突变，野生型sorC +等位基因可在反式中弥补这种缺陷，但对于极性插入则不能。因此，所有sor基因的单个启动子（SorC是其激活剂）似乎位于sorC之前。通过用sorC +等位基因互补组成型sorC等位基因，证明了SorC的阻遏活性，导致所有sor基因（包括sorC）的诱导表达，如通过一系列lacZ融合所观察到的，因此它作为激活剂和阻遏剂自动调节其表达。
