Institut Pasteur, Unité des Aspergillus, Département Parasitologie et Mycologie, 25 rue du Docteur Roux, F-75015 Paris.
J Biol Chem. 2013 May 10;288(19):13387-96. doi: 10.1074/jbc.M112.440172. Epub 2013 Mar 18.
SUN proteins are involved in yeast morphogenesis, but their function is unknown.
SUN protein plays a role in the Aspergillus fumigatus morphogenesis. Biochemical properties of recombinant SUN proteins were elucidated.
Both Candida albicans and Aspergillus fumigatus sun proteins show a β-(1,3)-glucanase activity.
The mode of action of SUN proteins on β-(1,3)-glucan is unique, new, and original. In yeasts, the family of SUN proteins has been involved in cell wall biogenesis. Here, we report the characterization of SUN proteins in a filamentous fungus, Aspergillus fumigatus. The function of the two A. fumigatus SUN genes was investigated by combining reverse genetics and biochemistry. During conidial swelling and mycelial growth, the expression of AfSUN1 was strongly induced, whereas the expression of AfSUN2 was not detectable. Deletion of AfSUN1 negatively affected hyphal growth and conidiation. A closer examination of the morphological defects revealed swollen hyphae, leaky tips, intrahyphal growth, and double cell wall, suggesting that, like in yeast, AfSun1p is associated with cell wall biogenesis. In contrast to AfSUN1, deletion of AfSUN2 either in the parental strain or in the AfSUN1 single mutant strain did not affect colony and hyphal morphology. Biochemical characterization of the recombinant AfSun1p and Candida albicans Sun41p showed that both proteins had a unique hydrolysis pattern: acting on β-(1,3)-oligomers from dimer up to insoluble β-(1,3)-glucan. Referring to the CAZy database, it is clear that fungal SUN proteins represent a new family of glucan hydrolases (GH132) and play an important morphogenetic role in fungal cell wall biogenesis and septation.
SUN 蛋白参与酵母形态发生，但它们的功能未知。
SUN 蛋白在烟曲霉形态发生中起作用。阐明了重组 SUN 蛋白的生化特性。
白色念珠菌和烟曲霉的 sun 蛋白均显示 β-(1,3)-葡聚糖酶活性。
SUN 蛋白对 β-(1,3)-葡聚糖的作用方式是独特的、新颖的和原创的。在酵母中，SUN 蛋白家族已参与细胞壁生物发生。在这里，我们报告了丝状真菌烟曲霉中 SUN 蛋白的特征。通过结合反向遗传学和生物化学，研究了两个烟曲霉 SUN 基因的功能。在分生孢子膨胀和菌丝生长过程中，AfSUN1 的表达强烈诱导，而 AfSUN2 的表达无法检测到。AfSUN1 的缺失对菌丝生长和产孢有负面影响。对形态缺陷的更仔细检查表明，菌丝肿胀、尖端泄漏、菌丝内生长和双层细胞壁，表明与酵母一样，AfSun1p 与细胞壁生物发生有关。与 AfSUN1 相反，在亲本菌株或 AfSUN1 单突变体菌株中缺失 AfSUN2 均不影响菌落和菌丝形态。重组 AfSun1p 和白色念珠菌 Sun41p 的生化特性表明，这两种蛋白质都具有独特的水解模式：作用于从二聚体到不溶性β-(1,3)-葡聚糖的β-(1,3)-寡聚物。参考 CAZy 数据库，很明显真菌 SUN 蛋白代表了一种新的葡聚糖水解酶家族（GH132），并在真菌细胞壁生物发生和隔膜形成中发挥重要的形态发生作用。
