I will apologise ahead of my very basic question.

I just read about Flagella Structure and learned that there are 4 rings, namely "L Ring", "P Ring", "MS Ring", "C Ring".

I tried looking online for why the rings are named as such, but i could not find anything related to their naming.

I am guessing L Ring = lipid ring? P Ring = Periplasm ring? MS Ring? C Ring = Cytoplasm ring?

Thank you in advance for enlightening me.


1 Answer 1


Your guesses are correct. More detailed, assuming you are referring to Gram-negative bacterial flagella and flagellar motor structure:

  1. L ring associates with the Lipopolysaccharides (more general S-layer for archaea and Gram-positive bacteria)
  2. P ring associates with the Peptidoglycan layer
  3. MS ring is embedded in the plasma Membrane (not sure why S maybe tranSmembrane?)
  4. C ring is a Cytoplasmic protein attached to the MS ring acting together as the rotor of the flagellar motor

As a structural biologist here is some recommended literature on high-resolution (cryo-EM) structures of flagellar proteins:

Molecular architecture of the bacterial flagellum.


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