Keiichi Namba

Biophysics and Physicobiology

Cryo-EM structure of CYP2C9 reveals a dimer-of-trimers assembly

Human cytochrome P450 2C9 (CYP2C9) is a hepatic microsomal enzyme involved in the oxidative metabolism of clinically important drugs, but the structural organization of its oligomeric assemblies outside crystallographic packing environments remains poorly understood. Here, we report the cryo-EM structure of human CYP2C...

Structural basis for substrate specificity switching revealed by the FlhA(A489E) suppressor mutation

The flagellar type III secretion system (fT3SS) switches its substrate specificity from hook-type to filament-type upon completion of hook assembly. This process is regulated by the coordinated actions of FliK, FlhB, and FlhA, but the structural mechanism underlying substrate specificity switching remains unclear. Here...

Haloplasma MreB reconstitution in a minimal synthetic bacterium reveals orthogonal force directions underlying distinct Mollicute motility systems

MreB, a bacterial actin homolog, is widely conserved in bacteria where it functions as a scaffold for a peptidoglycan synthesis. Intriguingly, members of the cell wall-lacking Mollicutes retain multiple mreB genes despite the absence of peptidoglycan. Previous work demonstrated that two MreB isoforms from Spiroplasma c...

Structural characterization of a pseudaminic acid-modified lateral flagellar filament from Vibrio alginolyticus

It is demonstrated that the Vibrio lateral flagellar filament is extensively modified by pseudaminic acid and that Maf is required for filament formation, the first structural characterization of a glycosylated Vibrio lateral flagellar filament and a close link between flagellin glycosylation and motility organelle ass...

ADP-Bound States of Cytoplasmic Dynein: Cryo-electron Microscopy Reveals a Two-Step Post-Power-Stroke Transition and Roles of Regulatory ATPase Sites.

These findings provide a mechanistic model in which coordinated conformational dynamics across multiple ATPase sites govern dynein's chemomechanical cycle and suggest a dynamic equilibrium between two ADP-bound states.

FlgJ cell-wall hydrolyzing activity enhances, but is not required, for flagellum assembly in Salmonella enterica

Salmonella can assemble functional flagella, even when the acetylglucosaminidase activity of FlgJ is genetically inactivated, showing that early steps in flagellar assembly are more diverse than previously thought and that differences in cell wall structure between gram-positive and -negative bacteria likely determine...