蓝细菌中不同的核心次要菌毛蛋白复合体启动特化的 IV 型菌毛组装
Distinct core minor pilin complexes prime specialized type IV filaments in cyanobacteria
通过对 90 个基因组开展结构系统发育分析，蓝细菌菌毛蛋白被划分为六个保守家族，并形成两个不同的推定核心启动复合体。在模式蓝细菌 Synechocystis sp. PCC 6803 中，这两个复合体分别启动两类形态不同的 IV 型菌毛组装：用于自然感受态的短而高动态菌毛，以及用于运动和趋光性的长黏附菌毛。结构分析显示 PilX 亚基含保守 beta-solenoid 结构域，作者提出其承担 PilY1 同源蛋白的封端功能。
来源：PLOS Genetics · journals.plos.org
by Nils Schuergers, Lars Wittig, Gen Enomoto, Julia Herz, Shamphavi Sivabalasarma, Katharina Ruoff, Friedel Drepper, Sonja-Verena Albers, Pitter F. Huesgen, Annegret Wilde
The model cyanobacterium, Synechocystis sp. PCC 6803 encodes in addition to the major pilin of the Type IV pilus filament, an extensive, partially uncharacterized repertoire of minor pilins. For those cyanobacterial minor pilins that have been characterized, their roles span a surprisingly diverse range of functions. To elucidate the roles of uncharacterized minor pilins in a systematic way, we applied structural phylogenomics across 90 genomes, classifying cyanobacterial pilins into six conserved families that form two distinct putative core priming complexes. We demonstrate that these complexes initiate the assembly of two morphologically distinct Type IV pilus filaments: short, hyper-dynamic pili for natural competence, and long, adhesive pili for motility and phototaxis. Structural analysis revealed a conserved beta-solenoid domain in PilX subunits, which we propose fulfills the capping function of PilY1 homologs. Proteomic data indicate that the minor pilin PilX2 facilitates the assembly of motility pili, which is required to maintain DnaJ3 co-chaperone levels and trigger cAMP-dependent surface sensing. These findings challenge the concept of a single multipurpose pilus, establishing that cyanobacteria utilize a shared machinery to assemble two specialized filaments, each primed by distinct core minor pilin complexes to meet the conflicting biophysical requirements of DNA uptake and surface motility.