Romeis T, Kämper J, Kahmann R
Institut für Genetik und Mikrobiologie der Universität München, Maria-Ward-Strasse 1a, 80638 Munich, Germany.
Proc Natl Acad Sci U S A. 1997 Feb 18;94(4):1230-4. doi: 10.1073/pnas.94.4.1230.
Pathogenic and sexual development of the fungus Ustilago maydis, the causal agent of corn smut disease, is regulated by heterodimerization of two unrelated homeodomain proteins bE and bW, both encoded by the multi-allelic b mating-type locus. This complex can only be formed if the two proteins are derived from different alleles. The heterodimer is believed to function as a transcriptional regulator that binds to target sites upstream of developmentally regulated genes. We have synthesized a translational fusion in which bE is tethered to bW by a designed flexible kink region. U. maydis strains expressing this synthetic b-fusion become pathogenic for corn illustrating that the single-chain fusion substitutes for the active bE/bW heterodimer. Synthetic b-fusions in which bE and bW originate from the same allele as well as fusions deleted for the dimerization domains were shown to be active while both homeodomains were required for function. Such active fusion proteins are expected to be instrumental in the identification of pathogenicity genes.
玉米瘤黑粉病的病原菌玉米黑粉菌（Ustilago maydis）的致病和有性发育由两个不相关的同源结构域蛋白bE和bW的异源二聚化调控，这两个蛋白均由多等位基因b交配型位点编码。只有当这两种蛋白来自不同等位基因时，这种复合体才能形成。据信，该异源二聚体作为转录调节因子，与发育调控基因上游的靶位点结合。我们合成了一种翻译融合体，其中bE通过设计的柔性扭结区域与bW相连。表达这种合成b融合体的玉米黑粉菌菌株对玉米具有致病性，这表明单链融合体替代了活性bE/bW异源二聚体。结果显示，bE和bW源自相同等位基因的合成b融合体以及缺失二聚化结构域的融合体具有活性，而两个同源结构域对于功能都是必需的。预计这种活性融合蛋白将有助于致病性基因的鉴定。
