| Category | Summary |
|---|---|
| Identity/Complex | UniProt Q88DZ5 is annotated as RecBCD enzyme subunit RecB from *Pseudomonas putida* KT2440; available mechanistic literature supports RecB as the helicase–nuclease subunit of the heterotrimeric RecBCD complex (RecB/RecC/RecD), also called Exonuclease V, with RecB carrying helicase/ATPase and nuclease-linked functions (pqac-00000000, pqac-00000001, pqac-00000027, pqac-00000030). |
| Enzymatic activities | RecB contributes ATP-dependent 3′→5′ translocation/helicase activity, while its C-terminal nuclease domain cleaves DNA in a Mg2+-dependent manner; after Chi recognition, RecBCD nicks the 3′-ended strand and promotes RecA loading onto the resulting 3′ ssDNA tail (pqac-00000023, pqac-00000026, pqac-00000028, pqac-00000029). |
| Substrates | RecBCD acts primarily on blunt or nearly blunt dsDNA ends, including two-ended DSBs and one-ended broken replication forks; during processing it unwinds duplex DNA and degrades emerging ssDNA to short oligonucleotides, ultimately generating recombinogenic 3′-tailed DNA (pqac-00000023, pqac-00000024, pqac-00000026, pqac-00000030). |
| Chi regulation | Canonical *E. coli* Chi is 5′-GCTGGTGG-3′ and triggers a switch from degradative to recombination-promoting processing; in *Pseudomonas syringae* Lz4W the cognate octamer is ChiPs 5′-GCTGGCGC-3′, showing that Chi recognition is species-specific within pseudomonads (pqac-00000023, pqac-00000024, pqac-00000025, pqac-00000029). |
| Pathway role | RecB functions in the major bacterial homologous recombination pathway for DSB repair, replication-fork rescue, and genome maintenance by helping RecBCD create a 3′ overhang and load RecA, followed by downstream RuvABC-mediated branch migration/resolution (pqac-00000024, pqac-00000026, pqac-00000027, pqac-00000030). |
| Localization | No direct localization study for Q88DZ5 in KT2440 was retrieved, but RecBCD acts on chromosomal DNA ends and stalled/broken replication forks; this supports a cytoplasmic, nucleoid-associated functional location rather than membrane or extracellular localization (pqac-00000023, pqac-00000026, pqac-00000030). |
| Pseudomonas-specific evidence | In *P. syringae* Lz4W, recB/recC/recD mutants are UV- and mitomycin C-sensitive, fail to grow at 4°C, and accumulate linear/fragmented chromosomal DNA; RecB and RecD ATPase/helicase activities are essential in vivo, whereas RecB nuclease activity is partly dispensable and can be compensated by RecJ in some contexts (pqac-00000003, pqac-00000004, pqac-00000006, pqac-00000007). |
| KT2440-specific evidence | Direct experimental evidence for PP_4673/Q88DZ5 in *P. putida* KT2440 is limited in the retrieved corpus. KT2440 studies instead show that DNA-damage tolerance and SOS-linked phenotypes can be assayed genetically in this strain, and that prophage-free KT2440 is more UV-tolerant without detectable change in RecA-mediated homologous recombination; these data provide pathway context but not a direct recB functional test (pqac-00000014, pqac-00000015, pqac-00000017). |
| Recent (2023-2024) advances | Recent work refined RecB-centered mechanism: a 2023 review synthesized mutant/structural evidence for RecB tethering, Chi-triggered conformational control, and inter-subunit signaling; a 2024 study showed the RecB nuclease domain can trans-complement truncated RecBCD, supporting a Chi-induced rearrangement that exposes the RecA-loading surface rather than a simple tethered “swing-out” model (pqac-00000023, pqac-00000027, pqac-00000028). |
| Quantitative stats | RecBCD is among the fastest/processive bacterial helicase–nucleases, reported at ~1 kb/s and ≥100 kb processivity in recent review literature; older review values cite ~300 bp/s depending on assay conditions. In *E. coli*, RecB is low abundance (~5 molecules/cell in one synthesis; ~3.9 ± 0.6 molecules/cell in a later single-cell study), indicating tight expression control for this potentially DNA-destructive activity (pqac-00000023, pqac-00000029, pqac-00000018, pqac-00000019). |


*Table: This table summarizes the evidence-supported functional annotation of RecB/RecBCD for *Pseudomonas putida* KT2440, while clearly separating broad conserved RecBCD biology from the more limited KT2440-specific evidence. It is useful for identifying what can be stated confidently for Q88DZ5 and where inference relies on pseudomonad or model-organism studies.*