Health Dictionary
Reliable, easy-to-read patient information on common medical conditions — written in plain language, free of jargon, and grounded in current evidence. Browse the most frequent diagnoses, understand what they mean for everyday life, and learn which steps and questions help you have a focused conversation with your doctor.
Flagellin
Introduction
Flagellin is a protein that arranges itself in a hollow cylinder to form the filament in bacterial flagellum. It has a mass of about 30,000 to 60,000 daltons. Flagellin is the principal substituent of bacterial flagellum, and is present in large amounts on nearly all flagellated bacteria.
Structure
Structure
The structure of flagellin is responsible for the helical shape of the flagellar filament, which is important for its proper function.
The N- and C-termini of flagellin form the inner core of the flagellin protein, and is responsible for flagellin’s ability to polymerize into a filament. The central portion of the protein makes up the outer surface of the flagellar filament. While the termini of the protein is quite similar between all bacterial flagellins, the central portion is wildly variable.
Immune response
Immune response
In mammals
Mammals often have acquired immune responses (T-cell and antibody responses) to flagellated bacterium occurs frequently to flagellar antigens. Some bacteria are able to switch between multiple flagellin genes in order to evade this response.
The propensity of the immune response to flagellin may be explained by two facts:
- First, flagellin is an extremely abundant protein in flagellated bacteria.
- Secondly, there exists a specific innate immune receptor that recognizes flagellin, Toll-like receptor 5 (TLR5).
In plants
In addition a 22 amino acid sequence (flg22) of the conserved N-terminal part of flagellin is known to activate plant defence mechanisms. Flagellin perception in Arabidopsis thaliana functions via the receptor-like-kinase, FLS2 (flagellin-sensitive-2)). Mitogen-activated-protein-kinases (MAPK) acts as signalling compounds and more than 900 genes are affected upon flg22 treatment.
Pre-stimulation with a synthetic flg22-peptide led to enhanced resistance against bacterial invaders.
External links
External links
- Flagellin at the US National Library of Medicine Medical Subject Headings (MeSH)
More detailed information: Research article: bacterial flagellin and plant disease resistance, published by Zipfel. et al (2004) ) Abstract Article