Maki-Yonekura, S., Yonekura, K. & Namba, K. Domain movements of HAP2 in the cap-filament complex formation and growth process of the bacterial flagellum. Proc. Natl Acad. Sci. USA 100, 15528-15533

Protonic NanoMachine Project, Exploratory Research for Advanced Technology, Japan Science and Technology Agency, 3-4 Hikaridai, Seika, Kyoto 619-0237, Japan.
Proceedings of the National Academy of Sciences (Impact Factor: 9.67). 01/2004; 100(26):15528-33. DOI: 10.1073/pnas.2534343100
Source: PubMed


The cap at the growing end of the bacterial flagellum is essential for its growth, remaining stably attached while permitting the insertion of flagellin transported from the cytoplasm through the narrow central channel. We analyzed the structure of the isolated cap in its frozen hydrated state by electron cryomicroscopy. The 3D density map now shows detailed features of domains and their connections, giving reliable volumes and masses, making assignment of the domains to the amino acid sequence possible. A model of the cap-filament complex built with an atomic model of the filament allows a quantitative analysis of the cap domain movements on cap binding and rotation that promotes the efficient self assembly of flagellin during the filament growth process.

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Available from: Koji Yonekura, Jun 19, 2014
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    • "The molecular structure of both L-type and R-type flagellin monomers is already known from electron cryomicroscopy [14], [15] and is also available from protein data bank. Some of the investigations in the past based on molecular dynamics (MD) simulations on the bacterial flagellum involved the motion of a rotating bacterial flagellum [16], the domain movement of the cap protein HAP2 from the viewpoint of flagellum growth [17] and the "
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    ABSTRACT: Magnetospirillum magneticum (AMB-1), which belong to alpha-protobacterium are gram-negative, single-celled prokaryotic organisms consisting of a lash-like cellular appendage called flagella. These filamentous structures are made up of a protein called flagellin that in turn consist of four sub-domains, two inner domains (D0, D1) made up of alpha-helices and two outer domains (D2, D3) made up of beta sheets. It is wrapped in a helical fashion around the longitudinal filament with the outermost sub-domain (D3) exposed to the surrounding environment. This study focuses on the interaction of the D3 with semiconducting as well as metallic single-walled carbon nanotubes (SWNT) and in turn presents the interactive forces between the SWNT and D3 from the perspective of size and type of SWNT. It is found that the SWNT interacts the most with glycine and threonine residues of flagellin both electrostatically as well as through van der waals. Further, the viability of magnetotactic bacteria Magnetospirillum magneticum (AMB-1) in the presence of SWNT is experimentally investigated and it is found that magnetotaxis in AMB-1 is preserved without any toxic effects due to SWNT. It is proposed that AMB-1 can be used as an efficient carrier of carbon nanotubes through its flagellum for nanofabrication tasks.
    36th Annual International IEEE EMBS Conference, Chicago, Illinois, USA; 08/2014
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    ABSTRACT: T he bacterial flagellum is a biological macromolecular nanomachine for locomotion. A membrane embedded molecular motor rotates a long helical filament that works as a pro‑ peller driving the bacterium through the liquid environment. The flagellum is composed of about 30 different proteins with copy numbers ranging from a few to a few thousands and is made by self‑assembly of those proteins. The helical filament can be transformed into various distinct supercoiled forms by changes in chemical environment, single amino acid mutations, or mechani‑ cal forces. The axial portion of the flagellum involves several substructures: the rod, the hook, the hook‑filament junction, the long helical filament and a cap at the filament tip. Although the axial component proteins are dissimilar at the primary sequence level, they share common structural characteristics. The central portions of their amino acid sequences are hypervariable whereas the amino‑ and carboxy‑terminal parts contain highly conserved segments. In their monomeric form, they posses large, natively‑disordered terminal regions that are essential in controlling and mediating intersubunit interactions. Recent structural studies—combining X‑ray diffraction and single particle image analysis by cryo‑EM—have given insights into the molecular mechanisms of self‑assembly, supercoiling and polymorphic ability and open the way for construction of various flagella‑based systems for applications in vaccination, bio‑ or nanotechnology.
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