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Revision as of 16:49, 30 December 2012
Contents |
STRUCTURE OF THE RECEPTOR-BINDING DOMAIN OF THE BACTERIOPHAGE T4 SHORT TAIL FIBRE
Description
Bacterophage T4 Description
Bacteriophage T4 belongs to the Myoviridae Family and to the Caudovirales Order because of their complex tail structure with a high number of proteins involved. It infects Escherichia coli bacteria. (image) Each bacteriophage T4 baseplate is composed of at least 16 different gene products, also called gp. These gene products can be divided into groups: the 6 long and the 6 short tail fibers (on the schematic rpresentation, they are not all shown). OLIGOMERIQUE They form a multiprotein machine which plays an important role at the first stage of a phage infection. It is essential for the host cell recognition, the attachment of the bacteriophage and the sheath contraction allowing viral DNA ejection.
Adsorption and penetration phases
First the viral particles recognize and bind reversibly to cell-surface lipopolysaccharide receptors thanks to six long tail fibers which are connected to the baseplate. The baseplate conformation changes: from a hexagon shape, it becomes a six-pointed star. This change can be the result of changing the interactions between the proteins.
It has two consequences. The first one is the unfolding of the short tail fibers, which are under the baseplate. Thus, they are able to attach irreversibly to the host cell surface. The second one is the induction of the tail sheath’s contraction. Afterwards the tail tube is driving through the cell membrane. The activated lysozyme domain of gp5 degraded the peptidoglycan layer. To finish, the phage DNA single-stranded is injected into the bacterial cytoplasm through the tail tube.
Role of the protein 1OCY
During the first step of the lytic cycle, the short tail fibers gp12 is attached to the host cell.
A monomer of gp12 has a mass of 55.3 kDa. It is composed of two proteins: 1H6W and 1OCY. Each short tail is composed of three repetition of the monomer. Thanks to a three-dimensional cryoelectron microscopy, a reconstruction of the baseplate was determined to a resolution of 12 A.
Interaction of the short tail fibers with each other and with the gp11 maintains the hexagon shape stability. The gp11 is also associated with gp10, which is clamped between the three fingers of gp11. This association between gp10 and gp11 is essential for the attachment of gp12 to the baseplate. When a rotation of gp11 around its three-fold axis occurs, the end of the short tail fiber is oriented toward the host cell surface.
After the creation of six wedge composed of 3 gp11, 3gp10, 1 gp7, 2 gp8, 2 gp6, gp25 and gp53, is the wedge associated to the hub. Then is 3 gp9 and 3gp12 added.
Structure
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References
Proteopedia Page Contributors and Editors
Anne-Lise Terrier, Bianca Waßmer
