Sharma Pratima, Mondal Alok K
Institute of Microbial Technology, Sector 39A, Chandigarh 160 036, India.
Biochem Biophys Res Commun. 2006 Jul 28;346(2):562-6. doi: 10.1016/j.bbrc.2006.05.155.
In eukaryotes, mitogen-activated protein kinase (MAPK) pathways are very important signal transduction modules that regulate various cellular processes. Although eukaryotic cells possess a number of MAP kinase pathways, normally the MAPKKs selectively activate their cognate MAPK. Recent studies suggest that the MAPK-docking site in MAPKK facilitates this specific recognition and activation. However, the role of the docking site under in vivo conditions has not been demonstrated. In yeast external high osmolarity activates HOG (high osmolarity glycerol) MAPK pathway that consists of MAPKKK (Ste11p or Ssk2p/Ssk22p), MAPKK (Pbs2p), and MAPK (Hog1p). Previously, we have isolated a Pbs2p homologue (Dpbs2p) from osmo-tolerant and salt-tolerant yeast Debaryomyces hansenii that complemented pbs2 mutation in Saccharomyces cerevisiae. Here we show, for the first time, the presence of a MAPK-docking domain in Dpbs2p that is essential for its function in vivo. Mutation in this motif completely abolished its binding to Hog1p in vitro.
在真核生物中，丝裂原活化蛋白激酶（MAPK）信号通路是调控各种细胞过程的重要信号转导模块。尽管真核细胞拥有多种MAP激酶信号通路，但通常情况下，MAPKK会选择性地激活其对应的MAPK。最近的研究表明，MAPKK中的MAPK对接位点有助于这种特异性识别和激活。然而，对接位点在体内条件下的作用尚未得到证实。在酵母中，外部高渗透压会激活HOG（高渗透压甘油）MAPK信号通路，该通路由MAPKKK（Ste11p或Ssk2p/Ssk22p）、MAPKK（Pbs2p）和MAPK（Hog1p）组成。此前，我们从耐渗透压和耐盐酵母汉逊德巴利酵母中分离出了一个Pbs2p同源物（Dpbs2p），它能够互补酿酒酵母中的pbs2突变。在此，我们首次表明，Dpbs2p中存在一个MAPK对接结构域，该结构域对其在体内的功能至关重要。该基序的突变完全消除了它在体外与Hog1p的结合。
