Gene Ontology annotation based on UniProtKB/Swiss-Prot keyword mapping
The tail sheath structure of bacteriophage T4: a molecular machine for infecting bacteria.
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gp18 forms the contractile tail sheath composed of 138 subunits surrounding the central tail tube and drives the tube through the host outer membrane during contraction via rigid-body subunit sliding.
"The sheath consists of 138 copies of the tail sheath protein, gene product (gp) 18, which surrounds the central non-contractile tail tube. The contraction of the sheath drives the tail tube through the outer membrane, creating a channel for the viral genome delivery."
UniProtKB record for P13332 (18_BPT4)
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gp18 is the structural subunit of the contractile tail sheath, assembling into 23 hexameric rings (138 copies) that contract during infection to drive the central tube through the host outer membrane.
"A total of 138 copies of gp18 arranged into 23 hexameric rings constitutes the sheath. During infection, contraction of the sheath drives the central tube through the host outer membrane, creating a channel for DNA ejection from the capsid into the host cell."
Deep research summary for Bacteriophage T4 gene 18 (gp18)
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gp18 polymerizes around the central tail tube to form the outer contractile sheath, which shortens from ~925 A to ~420 A during infection.
"The tail sheath is the outer contractile cylinder that wraps around a central, relatively rigid tail tube; gp18 is the major structural subunit that polymerizes to form this contractile sheath."