Instituto de Fisiología Celular, Universidad Nacional Autónoma de México, Mexico City, Mexico.
Instituto de Investigaciones Biomédicas, Universidad Nacional Autónoma de México, Mexico City, Mexico
J Bacteriol. 2018 Sep 24;200(20). doi: 10.1128/JB.00397-18. Print 2018 Oct 15.
In this work, we have characterized the soluble lytic transglycosylase (SltF) from that interacts with the scaffolding protein FlgJ in the periplasm to open space at the cell wall peptidoglycan heteropolymer for the emerging rod. The characterization of the genetic context of and s in alphaproteobacteria shows that these two separate genes coexist frequently in a flagellar gene cluster. Two domains of unknown function in SltF were studied, and the results show that the deletion of a 17-amino-acid segment near the N terminus does not show a recognizable phenotype, whereas the deletion of 47 and 95 amino acids of the C terminus of SltF disrupts the interaction with FlgJ without affecting the transglycosylase catalytic activity of SltF. These mutant proteins are unable to support swimming, indicating that the physical interaction between SltF and FlgJ is central for flagellar formation. In a maximum likelihood tree of representative lytic transglycosylases, all of the flagellar SltF proteins cluster in subfamily 1F. From this analysis, it was also revealed that the lytic transglycosylases related to the type III secretion systems present in pathogens cluster with the closely related flagellar transglycosylases. Flagellar biogenesis is a highly orchestrated event where the flagellar structure spans the bacterial cell envelope. The rod diameter of approximately 4 nm is larger than the estimated pore size of the peptidoglycan layer; hence, its insertion requires the localized and controlled lysis of the cell wall. We found that a 47-residue domain of the C terminus of the lytic transglycosylase (LT) SltF of is involved in the recognition of the rod chaperone FlgJ. We also found that in many alphaproteobacteria, the flagellar cluster includes a homolog of SltF and FlgJ, indicating that association of an LT with the flagellar machinery is ancestral. A maximum likelihood tree shows that family 1 of LTs segregates into seven subfamilies.
在这项工作中，我们描述了来自 的可溶性溶菌转糖基酶 (SltF)，它与周质中的支架蛋白 FlgJ 相互作用，在细胞壁肽聚糖杂聚物中开辟空间，为新兴的菌杆腾出空间。对α变形菌中的 和 s 的遗传背景进行了特征描述，结果表明这两个独立的基因经常共存于一个鞭毛基因簇中。研究了 SltF 中的两个未知功能域，结果表明，在 N 端附近缺失 17 个氨基酸片段不会表现出可识别的表型，而 C 端缺失 SltF 的 47 和 95 个氨基酸会破坏与 FlgJ 的相互作用，而不影响 SltF 的转糖基酶催化活性。这些突变蛋白无法支持游泳，表明 SltF 和 FlgJ 之间的物理相互作用是鞭毛形成的核心。在代表性溶菌转糖基酶的最大似然树中，所有鞭毛 SltF 蛋白都聚集在亚家族 1F 中。从这项分析中，还揭示了与病原体中存在的 III 型分泌系统相关的溶菌转糖基酶与密切相关的鞭毛转糖基酶聚类。鞭毛生物发生是一个高度协调的事件，鞭毛结构跨越细菌细胞包膜。棒状直径约为 4nm，大于估计的肽聚糖层的孔大小；因此，其插入需要细胞壁的局部和受控裂解。我们发现，来自 的溶菌转糖基酶 (LT) SltF 的 C 端 47 个残基的结构域参与了对杆状伴侣 FlgJ 的识别。我们还发现，在许多α变形菌中，鞭毛簇包括 SltF 和 FlgJ 的同源物，这表明 LT 与鞭毛机械的结合是祖先的。最大似然树显示，家族 1 的 LT 分为七个亚家族。
