ジャーナル: Nat Commun / 年: 2024 タイトル: Perturbed N-glycosylation of Halobacterium salinarum archaellum filaments leads to filament bundling and compromised cell motility. 著者: Shahar Sofer / Zlata Vershinin / Leen Mashni / Ran Zalk / Anat Shahar / Jerry Eichler / Iris Grossman-Haham / 要旨: The swimming device of archaea-the archaellum-presents asparagine (N)-linked glycans. While N-glycosylation serves numerous roles in archaea, including enabling their survival in extreme ...The swimming device of archaea-the archaellum-presents asparagine (N)-linked glycans. While N-glycosylation serves numerous roles in archaea, including enabling their survival in extreme environments, how this post-translational modification contributes to cell motility remains under-explored. Here, we report the cryo-EM structure of archaellum filaments from the haloarchaeon Halobacterium salinarum, where archaellins, the building blocks of the archaellum, are N-glycosylated, and the N-glycosylation pathway is well-resolved. We further determined structures of archaellum filaments from two N-glycosylation mutant strains that generate truncated glycans and analyzed their motility. While cells from the parent strain exhibited unidirectional motility, the N-glycosylation mutant strain cells swam in ever-changing directions within a limited area. Although these mutant strain cells presented archaellum filaments that were highly similar in architecture to those of the parent strain, N-linked glycan truncation greatly affected interactions between archaellum filaments, leading to dramatic clustering of both isolated and cell-attached filaments. We propose that the N-linked tetrasaccharides decorating archaellins act as physical spacers that minimize the archaellum filament aggregation that limits cell motility.
分子量: 20107.971 Da / 分子数: 25 / 由来タイプ: 天然 詳細: Since Hbt. salinarum encodes five archaellins (i.e., FlaA1, FlaA2, FlaB1, FlaB2, and FlaB3) and their arrangement within the archaellum filaments is unknown, we further refined the cryo-EM ...詳細: Since Hbt. salinarum encodes five archaellins (i.e., FlaA1, FlaA2, FlaB1, FlaB2, and FlaB3) and their arrangement within the archaellum filaments is unknown, we further refined the cryo-EM map without applying symmetry, in an attempt to resolve the positions of these archaellins within the filament, as done previously with reconstruction of the Methanocaldococcus villosus archaellum. Symmetry-free refinement improved the overall resolution map to 3.1 A and revealed differences in density among archaellin subunits. Nonetheless, we were unable to identify features that would allow us to unambiguously assign specific archaellins into the density, perhaps because the regions that distinguish each archaellin are few, short, and mostly predicted to lack defined secondary structure, or because the five archaellins are not organized in a repeating pattern. Consequently, we built a model into the central region of the cryo-EM map comprising 26 archaellin subunits that share a consensus sequence, in which identical residues among the five archaellins are explicitly modelled, with those variable residues usually being modelled as alanine residues (UNK). 由来: (天然) Halobacterium salinarum (好塩性)