| Aspect | Key findings | Key evidence source (author year) with DOI URL |
|---|---|---|
| Identity | The target matches bacteriophage T4 gene 2 product gp2, historically also called gp64; gene 2 and gene 64 map to the same ORF encoding a head-associated terminal DNA-protecting protein. (pqac-00000003, pqac-00000010, pqac-00000011) | Lipińska et al. 1989 — https://doi.org/10.1128/jb.171.1.488-497.1989; Wang et al. 2000 — https://doi.org/10.1128/jb.182.3.672-679.2000 |
| Size/basicity | gp2 is predicted to be ~27 kDa, migrates at ~30 kDa on SDS-PAGE, and is highly basic/rich in Lys and Arg; Wang et al. report a high predicted pI (~10.94). (pqac-00000003, pqac-00000005, pqac-00000002) | Lipińska et al. 1989 — https://doi.org/10.1128/jb.171.1.488-497.1989; Wang et al. 2000 — https://doi.org/10.1128/jb.182.3.672-679.2000 |
| Expression timing | gp2 synthesis is late during infection; Wang et al. note detectability after ~13 min at 37°C, consistent with a morphogenetic/virion-incorporated role rather than an early cytoplasmic antinuclease role. (pqac-00000004, pqac-00000008, pqac-00000010) | Wang et al. 2000 — https://doi.org/10.1128/jb.182.3.672-679.2000; Lipińska et al. 1989 — https://doi.org/10.1128/jb.171.1.488-497.1989 |
| Localization | gp2 is incorporated into the phage head, attached to the DNA terminus in the mature head, and proposed to reside at the head vertex/head-tail junction so it can accompany the DNA during injection. (pqac-00000003, pqac-00000006, pqac-00000008, pqac-00000009, pqac-00000011) | Lipińska et al. 1989 — https://doi.org/10.1128/jb.171.1.488-497.1989; Wang et al. 2000 — https://doi.org/10.1128/jb.182.3.672-679.2000 |
| Molecular function | gp2 has two experimentally supported functions: (1) protection of incoming T4 dsDNA ends from host RecBCD/ExoV degradation and (2) participation in normal head-to-tail joining during morphogenesis/reconstitution. (pqac-00000000, pqac-00000003, pqac-00000004, pqac-00000011) | Lipińska et al. 1989 — https://doi.org/10.1128/jb.171.1.488-497.1989; Wang et al. 2000 — https://doi.org/10.1128/jb.182.3.672-679.2000 |
| Mechanism evidence | Evidence favors direct action at phage DNA ends rather than generalized inhibition of RecBCD: cloned gp2 protects entering T4 DNA in vivo; virion gp2 protects natural termini in cis; plasmid-expressed gp2 can act in trans; timing effects show pre-existing gp2 improves rapid end protection. Authors interpret this as end binding/occlusion, though Lipińska et al. discuss analogy to anti-RecBCD systems and Wang et al. note no absolute proof that steric end-blocking is the only mechanism. (pqac-00000001, pqac-00000002, pqac-00000006, pqac-00000008, pqac-00000010) | Lipińska et al. 1989 — https://doi.org/10.1128/jb.171.1.488-497.1989; Wang et al. 2000 — https://doi.org/10.1128/jb.182.3.672-679.2000 |
| Mutant phenotypes | Gene 2 mutants show degraded injected DNA in ExoV+/RecBCD+ hosts, reduced burst size, fewer DNA-filled heads, impaired tail attachment/head-tail joining, and failure to grow on Su-/Su' hosts; restriction is suppressed in recBC-deficient hosts. More N-terminal lesions can worsen head-tail joining defects. (pqac-00000000, pqac-00000003, pqac-00000009, pqac-00000011) | Lipińska et al. 1989 — https://doi.org/10.1128/jb.171.1.488-497.1989; Wang et al. 2000 — https://doi.org/10.1128/jb.182.3.672-679.2000 |
| Quantitative data | Reported values include: predicted mass ~27,068 Da with apparent ~30 kDa; gp2 detected after ~13 min at 37°C; rgp2 increased total phage titer ~150-200-fold and phenotypic-21 titer up to ~500-fold in some reconstitution assays; maximal yields reached 2.5 × 10^9 phage/mL and 0.3 × 10^8 phenotypic-21 phage/mL; only ~15% of rgp2-reconstituted particles grew on an ExoV1 indicator in one assay; historical mutant infections yielded ~40 full heads/cell, ~20 empty heads/cell, ~0.07 infective phage/cell, and ~40 killer particles/cell. (pqac-00000000, pqac-00000002, pqac-00000004) | Wang et al. 2000 — https://doi.org/10.1128/jb.182.3.672-679.2000; Lipińska et al. 1989 — https://doi.org/10.1128/jb.171.1.488-497.1989 |


*Table: This table summarizes the experimentally supported functional annotation of bacteriophage T4 gene 2/gp2 (gp64; UniProt P15076) using only the provided evidence snippets from Lipińska et al. 1989 and Wang et al. 2000. It highlights identity verification, mechanism, localization, mutant phenotypes, and quantitative data relevant to annotation.*