The University of Osaka · Biochemistry, Genetics and Molecular Biology
Professor Keiichi Namba's research lab specializes in structural microbiology and molecular biophysics, focusing on the self-assembly and dynamic organization of complex macromolecular machines in bacteria. The lab investigates the structural basis of bacterial flagellar assembly, particularly the type III protein export system and rotary motor function, using advanced techniques such as X-ray fiber diffraction, cryo-electron microscopy, and live-cell fluorescence imaging. A central theme is understanding how protein conformational changes, disordered regions, and electrostatic interactions govern the precise assembly and regulation of large cellular structures like the flagellum and viral capsids. The lab also explores the role of proton translocation and stator dynamics in motor function, contributing to fundamental insights into energy transduction and nanomachine design in prokaryotes.
Figures are computed from collected data and may differ slightly.
X-ray fiber diffraction analysis of tobacco mosaic virus (TMV) has led to the building of a molecular model of the intact virus, based on a map at 3.6 A resolution derived from five separated Bessel orders. This has been made possible by advances in the solution of the fiber diffraction phase problem. It is now possible to understand much of the chemical basis of TMV assembly, particularly in terms of intersubunit electrostatic interactions and RNA binding. Consideration of the molecular structu
Flagellar type III protein export is highly organized and well controlled in a timely manner by dynamic, specific and cooperative interactions among components of the export apparatus, allowing the huge and complex macromolecular assembly to be built efficiently. The bacterial flagellum, which is required for motility, consists of a rotary motor, a universal joint and a helical propeller. Most of the flagellar components are translocated to the distal, growing end of the flagellum for assembly t
1. INTRODUCTION 2 2. OVERALL STRUCTURE AND SUBSTRUCTURES 5 2.1 Overall structure and components 5 2.2 Bidirectional rotary motor 5 2.3 Drive shaft 8 2.4 Bushing 8 2.5 Universal joint 9 2.6 Helical propeller 9 2.7 Axial junction 10 2.8 Capping structure 11 3. ASSEMBLY PROCESS OF THE FLAGELLUM 11 3.1 Step by step assembly 11 3.2 Flagellum-specific export apparatus and the channel 12 4. UNIQUE CHARACTERISTICS OF THE FLAGELLAR MOTOR DYNAMICS 13 5. STRUCTURAL DESIGN OF FLAGELLIN FOR ASSEMBLY REGULATI
From genes to cells there are many steps of hierarchical increments in building up complex frameworks that provide intricate networks of macromolecular interactions, through which cellular activities such as gene expression, signal processing, energy transduction and material conversion are dynamically organized and regulated. The self-assembly of macromolecules into large complexes is one such important step, but this process is by no means a simple aggregation of macromolecules with predefined
MotA and MotB form a transmembrane proton channel that acts as the stator of the bacterial flagellar motor to couple proton flow with torque generation. The C-terminal periplasmic domain of MotB plays a role in anchoring the stators to the motor. However, it remains unclear where their initial binding sites are. Here, we constructed Salmonella strains expressing GFP-MotB and MotA-mCherry and investigated their subcellular localization by fluorescence microscopy. Neither the D33N and D33A mutatio
The bacterial flagellar export apparatus is required for the construction of the bacterial flagella beyond the cytoplasmic membrane. The membrane-embedded part of the export apparatus, which consists of FlhA, FlhB, FliO, FliP, FliQ and FliR, is located in the central pore of the MS ring formed by 26 copies of FliF. The C-terminal cytoplasmic domain of FlhA is located in the centre of the cavity within the C ring made of FliG, FliM and FliN. FlhA interacts with FliF, but its assembly mechanism re
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