Department of Biological Sciences, 181 Lapham Hall, University of Wisconsin-Milwaukee, 3209 N. Maryland Ave., Milwaukee, WI 53211, USA.
J Bacteriol. 2011 Feb;193(3):599-610. doi: 10.1128/JB.01203-10. Epub 2010 Dec 3.
Cells of Flavobacterium johnsoniae move rapidly over surfaces by a process known as gliding motility. Gld proteins are thought to comprise the gliding motor that propels cell surface adhesins, such as the 669-kDa SprB. A novel protein secretion apparatus called the Por secretion system (PorSS) is required for assembly of SprB on the cell surface. Genetic and molecular analyses revealed that sprB is part of a seven-gene operon spanning 29.3 kbp of DNA. In addition to sprB, three other genes of this operon (sprC, sprD, and sprF) are involved in gliding. Mutations in sprB, sprC, sprD, and sprF resulted in cells that failed to form spreading colonies on agar but that exhibited some motility on glass in wet mounts. SprF exhibits some similarity to Porphyromonas gingivalis PorP, which is required for secretion of gingipain protease virulence factors via the P. gingivalis PorSS. F. johnsoniae sprF mutants produced SprB protein but were defective in localization of SprB to the cell surface, suggesting a role for SprF in secretion of SprB. The F. johnsoniae PorSS is involved in secretion of extracellular chitinase in addition to its role in secretion of SprB. SprF was not needed for chitinase secretion and may be specifically required for SprB secretion by the PorSS. Cells with nonpolar mutations in sprC or sprD produced and secreted SprB and propelled it rapidly along the cell surface. Multiple paralogs of sprB, sprC, sprD, and sprF are present in the genome, which may explain why mutations in sprB, sprC, sprD, and sprF do not result in complete loss of motility and suggests the possibility that semiredundant SprB-like adhesins may allow movement of cells over different surfaces.
黄杆菌属的细胞通过一种称为滑行运动的过程在表面上快速移动。Gld 蛋白被认为组成了推动细胞表面黏附物（如 669kDa 的 SprB）的滑行马达。一种称为 Por 分泌系统（PorSS）的新型蛋白分泌装置是 SprB 在细胞表面组装所必需的。遗传和分子分析表明，sprB 是跨越 DNA 29.3 kbp 的七个基因操纵子的一部分。该操纵子的除 sprB 之外的另外三个基因（sprC、sprD 和 sprF）也参与滑行。sprB、sprC、sprD 和 sprF 的突变导致细胞在琼脂上无法形成扩展菌落，但在湿载玻片上的玻璃上表现出一定的运动性。SprF 与牙龈卟啉单胞菌 PorP 有一些相似之处，PorP 是通过牙龈卟啉单胞菌 PorSS 分泌牙龈蛋白酶毒力因子所必需的。F. johnsoniae sprF 突变体产生 SprB 蛋白，但 SprB 定位到细胞表面的能力有缺陷，表明 SprF 在 SprB 的分泌中起作用。F. johnsoniae PorSS 除了在 SprB 的分泌中起作用外，还参与细胞外几丁质酶的分泌。SprF 不是几丁质酶分泌所必需的，可能专门通过 PorSS 分泌 SprB 所必需的。sprC 或 sprD 非极性突变的细胞产生和分泌 SprB，并使其沿细胞表面快速推进。sprB、sprC、sprD 和 sprF 的多个基因副本存在于基因组中，这可以解释为什么 sprB、sprC、sprD 和 sprF 的突变不会导致运动性完全丧失，并表明半冗余的 SprB 样黏附物可能允许细胞在不同表面上移动的可能性。
