Instituto de Bioquímica Vegetal y Fotosíntesis, Consejo Superior de Investigaciones Científicas and Universidad de Sevilla, Américo Vespucio 49, E-41092 Seville, Spain.
Mol Microbiol. 2010 Mar;75(5):1159-70. doi: 10.1111/j.1365-2958.2009.07031.x.
Anabaena sp. strain PCC 7120 is a filamentous cyanobacterium that can fix N(2) in differentiated cells called heterocysts, which exchange nutritional and regulatory compounds with the neighbouring photosynthetic vegetative cells. The cells in the filament appear to be joined by some protein structures, of which SepJ (FraG) that is located at the cell poles in the intercellular septa and is needed for filament integrity seems to be a component. Other known proteins required for filament integrity include FraC and FraH. Whereas fraC (alr2392) was constitutively expressed as an operon together with two downstream genes, alr2393 (fraD) and alr2394 (fraE), fraH (alr1603) was induced under nitrogen deprivation. Single mutants of these genes showed filament fragmentation under nitrogen deprivation and did not grow diazotrophically, although they formed heterocysts. The fraC and fraD mutants showed an impaired localization of SepJ at the intercellular septa and were hampered in the intercellular transfer of the fluorescent probe calcein. As shown with GFP fusions, FraC and FraD are also located at the intercellular septa. Therefore, at least three different proteins, SepJ, FraC and FraD, influence the architecture and function of the intercellular septa in the Anabaena filaments.
鱼腥藻 PCC 7120 是一种丝状蓝藻，能够在称为异形胞的分化细胞中固定 N(2)，异形胞与相邻的光合营养细胞交换营养和调节化合物。丝状体中的细胞似乎通过一些蛋白质结构连接在一起，其中位于细胞极的 SepJ（FraG）似乎是组成部分，它位于细胞间隔的细胞极，是丝状体完整性所必需的。其他已知的丝状完整性所必需的蛋白质包括 FraC 和 FraH。虽然 fraC（alr2392）与两个下游基因 alr2393（fraD）和 alr2394（fraE）一起作为操纵子组成型表达，但 fraH（alr1603）在氮饥饿下被诱导。这些基因的单突变体在氮饥饿下表现出丝状片段化，并且不能进行固氮生长，尽管它们形成了异形胞。 fraC 和 fraD 突变体在细胞间隔处的 SepJ 定位受损，并且在荧光探针 calcein 的细胞间转移中受阻。如 GFP 融合所示，FraC 和 FraD 也位于细胞间隔处。因此，至少有三种不同的蛋白质，SepJ、FraC 和 FraD，影响鱼腥藻丝状体中细胞间隔的结构和功能。
