Gene Ontology annotation through association of InterPro records with GO terms
Gene Ontology annotation based on UniProtKB/Swiss-Prot keyword mapping
Combined Automated Annotation using Multiple IEA Methods
The C-terminal fragment of the precursor tail lysozyme of bacteriophage T4 stays as a structural component of the baseplate after cleavage.
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Precursor gp5 (63 kDa) is cleaved into a 43-kDa N-terminal mature tail lysozyme fragment and a trimeric beta-structured C-terminal fragment that both remain in the assembled phage tail baseplate.
"Tail-associated lysozyme of bacteriophage T4 (tail lysozyme), the product of gene 5 (gp 5), is an essential structural component of the hub of the phage baseplate. It is synthesized as a 63-kDa precursor, which later cleaves to form mature gp 5 with a molecular weight of 43,000."
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The precursor or nicked gp5 complex exhibits approximately 10% of the lysozyme activity of isolated mature gp5*.
"The lysozyme activity of the precursor or the nicked protein is about 10% of that of mature gp 5."
Structure of the cell-puncturing device of bacteriophage T4.
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The 2.9 A crystal structure of the (gp5-gp27)3 complex reveals three domains in gp5, including an N-terminal antiparallel beta-barrel that binds inside the gp27 cylinder, a peripheral lysozyme domain, and a C-terminal triple-stranded beta-helix membrane-puncturing needle.
"The carboxy-terminal domain of gp5 is a triple-stranded beta-helix that forms an equilateral triangular prism, which acts as a membrane-puncturing needle. The middle lysozyme domain of gp5, situated on the periphery of the prism, serves to digest the peptidoglycan layer. The amino-terminal, antiparallel beta-barrel domain of gp5 is inserted into a cylinder formed by three gp27 monomers, which may serve as a channel for DNA ejection."
Control of bacteriophage T4 tail lysozyme activity during the infection process.
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Post-translational cleavage of gp5 between residues 351 and 352 and subsequent dissociation of the C-terminal needle relieve autoinhibition of the lysozyme active site by an adjacent monomer loop.
"The lysozyme activity is inhibited in the wild-type structure by a loop from the adjacent gp5 monomer that binds into the substrate-binding site. The same inhibition is apparent in the mutant structure, showing that the lysozyme is inhibited before gp5 is cleaved and, presumably, the lysozyme is activated only after gp5 has penetrated the outer membrane."
Structure of the T4 baseplate and its function in triggering sheath contraction.
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Atomic structure of the T4 baseplate resolves the central spike complex at the distal end of the tail tube.
"Here we present the atomic structure of the approximately 6-megadalton bacteriophage T4 baseplate in its pre- and post-host attachment states and explain the events that lead to sheath contraction in atomic detail."
Isolation and characterization of the bacteriophage T4 tail-associated lysozyme.
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Purified tail-associated lysozyme was identified as baseplate hub protein gp5 and shown to possess N-acetylmuramidase activity with a pH optimum near 5.8.
"Direct evidence has been obtained that the tail-associated lysozyme of bacteriophage T4 (tail-lysozyme) is gp5, which is a protein component of the hub of the baseplate."
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Tail-associated gp5 locally digests the host peptidoglycan layer to permit tail tube penetration into the periplasmic space.
"The tail-lysozyme has N-acetylmuramidase activity and the same substrate specificity as gene e lysozyme; the optimum pH is around 5.8, about 1 pH unit lower than for the e lysozyme. We assume that the tail-lysozyme plays an essential role in locally digesting the peptidoglycan layer to let the tube penetrate into the periplasmic space."
UniProtKB record for P16009 (BP05_BPT4)
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gp5 is a baseplate central spike lysozyme required for localized bacterial cell wall hydrolysis during phage DNA ejection.
"Baseplate central spike complex-associated lysozyme that is essential for the localized hydrolysis of bacterial cell wall, so that the tail tube, through which the phage DNA is ejected, can penetrate to the host inner membrane"
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Three copies of cleaved gp5* and gp5C assemble with three copies of gp27 and one copy of gp5.4 to form the central spike complex of the baseplate.
"The central spike complex, which creates an extension of the tail tube, is made up of three copies of the gp27-gp5*-gp5C complex and one copy of gp5.4"
Deep research report on bacteriophage T4 gene 5 (gp5; P16009)
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The (gp27-gp5*-gp5C)3 complex forms the central puncturing device of the T4 baseplate hub.
"In T4, the central puncturing device is formed by a **(gp27–gp5*–gp5C)3** complex, which aligns with and extends the tail tube to form a penetration and DNA-translocation path."
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During tail contraction, the C-terminal beta-helix needle of gp5 punctures the outer envelope while its muramidase domain cleaves NAM-NAG beta(1->4) bonds in peptidoglycan.
"During adsorption-triggered tail contraction, the gp5 C-terminal β-helix needle is driven into the host envelope, while gp5’s lysozyme-like domain (muramidase; EC 3.2.1.17) locally cleaves peptidoglycan (NAM–NAG β(1→4) linkage) to facilitate tail tube penetration and DNA injection."