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Flagellin
 
 
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Flagellin is a protein
Protein

Proteins are organic compounds made of amino acids arranged in a linear chain and joined together by peptide bonds between the carboxyl and amino groups of adjacent amino acid Residue ....
 that arranges itself in a hollow cylinder to form the filament in bacteria
Bacteria

The Bacteria are a large group of unicellular microorganisms. Typically a few micrometres in length, bacteria have a wide range of shapes, ranging from spheres to rods and spirals....
l flagellum
Flagellum

A flagellum is a tail-like structure that projects from the cell body of certain prokaryotic and eukaryotic cells, and it functions in locomotion....
. It has a mass of about 30,000 to 60,000 daltons
Atomic mass unit

The unified atomic mass unit , or dalton or, sometimes, universal mass unit, is a Units of measurement of mass used to express atomic weight and molecular masses....
. Flagellin is the principal substituent of bacterial flagellum
Flagellum

A flagellum is a tail-like structure that projects from the cell body of certain prokaryotic and eukaryotic cells, and it functions in locomotion....
, and is present in large amounts on nearly all flagellated bacteria.

structure of flagellin is responsible for the helical
Helix

A helix is a special kind of space curve, i.e. a Differentiable manifold curve in three-space. As a mental image of a helix one may take the spring ....
 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 polymer
Polymer

A polymer is a large molecule composed of repeating structural units typically connected by covalent chemical bonds. While polymer in popular usage suggests plastic, the term actually refers to a large class of natural and synthetic materials with a variety of properties....
ize into a filament.






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Encyclopedia


Empylori
Flagellin is a protein
Protein

Proteins are organic compounds made of amino acids arranged in a linear chain and joined together by peptide bonds between the carboxyl and amino groups of adjacent amino acid Residue ....
 that arranges itself in a hollow cylinder to form the filament in bacteria
Bacteria

The Bacteria are a large group of unicellular microorganisms. Typically a few micrometres in length, bacteria have a wide range of shapes, ranging from spheres to rods and spirals....
l flagellum
Flagellum

A flagellum is a tail-like structure that projects from the cell body of certain prokaryotic and eukaryotic cells, and it functions in locomotion....
. It has a mass of about 30,000 to 60,000 daltons
Atomic mass unit

The unified atomic mass unit , or dalton or, sometimes, universal mass unit, is a Units of measurement of mass used to express atomic weight and molecular masses....
. Flagellin is the principal substituent of bacterial flagellum
Flagellum

A flagellum is a tail-like structure that projects from the cell body of certain prokaryotic and eukaryotic cells, and it functions in locomotion....
, and is present in large amounts on nearly all flagellated bacteria.

Structure

The structure of flagellin is responsible for the helical
Helix

A helix is a special kind of space curve, i.e. a Differentiable manifold curve in three-space. As a mental image of a helix one may take the spring ....
 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 polymer
Polymer

A polymer is a large molecule composed of repeating structural units typically connected by covalent chemical bonds. While polymer in popular usage suggests plastic, the term actually refers to a large class of natural and synthetic materials with a variety of properties....
ize 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


In mammals

Mammal
Mammal

Mammals are a class of vertebrate animals whose name is derived from their distinctive feature, mammary glands, with which they feed their young....
s often have acquired immune response
Immune system

An immune system is a collection of biological processes within an organism that protects against disease by identifying and killing pathogens and tumour cells....
s (T-cell and antibody
Antibody

Antibodies are gamma globulin proteins that are found in blood or other bodily fluids of vertebrates, and are used by the immune system to identify and neutralize foreign objects, such as bacterium and viruses....
 responses) to flagellated bacterium occurs frequently to flagellar antigens. Some bacteria are able to switch between multiple flagellin gene
Gene

A gene is the basic unit of heredity in a living organism. All living things depend on genes. Genes hold the information to build and maintain their cell and pass genetic trait to offspring....
s 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
    Immune receptor

    An immune receptor is a Receptor , usually on a cell membrane, which binds to a substance and causes a response in the immune system....
     that recognizes flagellin, Toll-like receptor
    Toll-like receptor

    Toll-like receptors are a class of proteins that play a key role in the innate immune system. They are single membrane-spanning non-catalytic Receptor that recognize structurally conserved molecules derived from microbes....
     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
Arabidopsis thaliana

Arabidopsis thaliana , is a small flowering plant native to Europe, Asia, and northwestern Africa. A spring annual with a relatively short life cycle, Arabidopsis is popular as a model organism in plant biology and genetics....
 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


More detailed information: Research article: bacterial flagellin and plant disease resistance, published by Zipfel. et al. (2004)