Søgaard-Andersen L, Kaiser D
Department of Biochemistry, Standford University School of Medicine, CA 94305, USA.
Proc Natl Acad Sci U S A. 1996 Apr 2;93(7):2675-9. doi: 10.1073/pnas.93.7.2675.
C factor, an intercellular signaling protein, is required for aggregation and sporulation of the social bacterium, Myxococcus xanthus. We report that C factor, which normally is associated with the cell surface, provides input to the Frz signal transduction cascade. Elements of this cascade have sequence homology to bacterial chemotaxis systems and are known to control the frequency of gliding reversal. Exposure of developing cells of a C-factor-less mutant (csgA) to purified C factor increases the ratio of methylated to nonmethylated FrzCD protein, the Frz homolog of the methyl-accepting chemotaxis proteins. Methylation depends on the cognate methyltransferase FrzF, and its extent increases with the concentration of C factor. C-factor-induced methylation also depends on the product of a gene, called class II, which is necessary in vivo for all known responses to C factor. A model for aggregation is proposed in which C factor stimulates the Frz cascade and thereby decreases cell reversals in a way that preferentially leads cells into an aggregate.
C因子是一种细胞间信号蛋白，是群居细菌黄色粘球菌聚集和形成孢子所必需的。我们报告称，通常与细胞表面相关的C因子为Frz信号转导级联提供输入。该级联的元件与细菌趋化系统具有序列同源性，并且已知可控制滑行逆转的频率。将无C因子突变体（csgA）的发育细胞暴露于纯化的C因子中，会增加甲基化与未甲基化的FrzCD蛋白的比例，FrzCD蛋白是甲基接受趋化蛋白的Frz同源物。甲基化依赖于同源甲基转移酶FrzF，其程度随C因子浓度的增加而增加。C因子诱导的甲基化还依赖于一个名为II类基因的产物，该基因在体内是对C因子的所有已知反应所必需的。提出了一种聚集模型，其中C因子刺激Frz级联反应，从而以优先引导细胞形成聚集体的方式减少细胞逆转。
