| Aspect | Key findings | Evidence type (review/primary) | Experimental system (if applicable) | Source (author year journal) | URL/DOI | Citation id placeholder |
|---|---|---|---|---|---|---|
| Identity/domains | SlrP is the *Salmonella enterica* serovar Typhimurium Salmonella leucine-rich repeat protein, a member of the NEL (novel E3 ligase) family with an N-terminal LRR/LPX substrate-recognition region and a C-terminal catalytic NEL domain; one source notes a catalytic cysteine at C546 and ~10–11 LRRs. | Review + primary | Comparative/domain analyses; family summaries | Pillay et al. 2023 *Microbiology*; Bullones-Bolaños et al. 2022 *Biology*; Dubrule 2024 | https://doi.org/10.1099/mic.0.001342; https://doi.org/10.3390/biology11101517; https://doi.org/10.7939/r3-sw4j-1k92 | (pqac-00000000, pqac-00000003, pqac-00000010) |
| Secretion/translocation | SlrP is translocated into host cells by both SPI-1/T3SS1 and SPI-2/T3SS2. In macrophages, translocation shows timing dependence: T3SS1 contributes early (1 h p.i.) and T3SS2 later (6–8 h p.i.); native-promoter SlrP is detectable at both short and long infection times. | Review + primary | CyaA' translocation assays in HeLa, RAW264.7, NRK cells; SPI mutants (e.g., *ssaV*, *prgH*) | Cordero-Alba & Ramos-Morales 2014 *Journal of Bacteriology*; Pillay et al. 2023 *Microbiology*; Bullones-Bolaños et al. 2024 *Frontiers in Immunology* | https://doi.org/10.1128/jb.02158-14; https://doi.org/10.1099/mic.0.001342; https://doi.org/10.3389/fimmu.2024.1328707 | (pqac-00000009, pqac-00000018, pqac-00000011) |
| Regulation | *slrP* expression is optimal under intravacuolar-like, SPI2-inducing conditions (low pH/low Mg2+). Regulators identified include PhoQ/PhoP, LeuO, and Lon; PhoP directly activates transcription under SPI2-inducing conditions, while LeuO and Lon act through HilD under SPI1-inducing conditions. In vivo expression in macrophages requires PhoP. | Primary + recent primary synthesis | lac/lux transcriptional fusions, 3xFLAG immunoblotting, promoter mapping, infection assays | Cordero-Alba & Ramos-Morales 2014 *Journal of Bacteriology*; Bullones-Bolaños et al. 2024 *Frontiers in Immunology* | https://doi.org/10.1128/jb.02158-14; https://doi.org/10.3389/fimmu.2024.1328707 | (pqac-00000009, pqac-00000011, pqac-00000014) |
| Enzymatic mechanism | SlrP is a bacterial E3 ubiquitin ligase (EC 2.3.2.27) of the NEL family. NEL ligases act via a HECT-like transthiolation mechanism involving a catalytic cysteine and autoinhibition relieved by substrate/ubiquitin-dependent conformational change of the LRR region. SlrP ubiquitinates thioredoxin and SNRPD2; SNRPD2 shows a polyubiquitination ladder in vitro. SlrP-specific ubiquitin linkage preference was not established in the cited evidence. | Review + primary | In vitro ubiquitination assays with purified proteins; mechanistic family comparisons | Pillay et al. 2023 *Microbiology*; Bullones-Bolaños et al. 2022 *Biology*; Dubrule 2024 | https://doi.org/10.1099/mic.0.001342; https://doi.org/10.3390/biology11101517; https://doi.org/10.7939/r3-sw4j-1k92 | (pqac-00000000, pqac-00000001, pqac-00000003, pqac-00000007) |
| E2 partners | The reported host E2 partner for SlrP is Ube2D2; broader NEL-family summaries note preference for UBE2D-family enzymes. | Review + mechanistic synthesis | Ubiquitination pathway mapping in reviews | Pillay et al. 2023 *Microbiology*; Dubrule 2024 | https://doi.org/10.1099/mic.0.001342; https://doi.org/10.7939/r3-sw4j-1k92 | (pqac-00000000, pqac-00000018, pqac-00000003) |
| Host substrates/interaction partners | Supported host partners/substrates include thioredoxin/Trx1 (ubiquitinated; activity reduced), ERdj3 (binds in ER; interferes with folding), and SNRPD2 (specific ubiquitination substrate among Salmonella NELs). A 2024 study reports 14 new SlrP interactors from a screen, with SNRPD2 validated. Interaction with TRIM32 was mentioned in a review snippet, but no mechanistic significance was established in the provided evidence. | Review + primary | Yeast two-hybrid, pull-downs, HeLa/HEK293T expression, purified-protein assays, mass spectrometry | Bullones-Bolaños et al. 2022 *Biology*; Bullones-Bolaños et al. 2024 *Frontiers in Immunology*; Pillay et al. 2023 *Microbiology* | https://doi.org/10.3390/biology11101517; https://doi.org/10.3389/fimmu.2024.1328707; https://doi.org/10.1099/mic.0.001342 | (pqac-00000001, pqac-00000004, pqac-00000007, pqac-00000010, pqac-00000013) |
| Cellular localization | After translocation, SlrP localizes mainly to the host cytosol and partially to the endoplasmic reticulum; ER localization is consistent with ERdj3 interaction. | Primary | Host-cell localization studies summarized in expression/translocation work | Cordero-Alba & Ramos-Morales 2014 *Journal of Bacteriology* | https://doi.org/10.1128/jb.02158-14 | (pqac-00000009) |
| Phenotypes/biological role | Reported roles include promotion of host cell death/cytotoxicity, contribution to virulence in vivo, inhibition of antigen presentation in dendritic cells, and possible prevention of host anorexia via inflammasome inhibition; however, for several phenotypes the direct substrate-to-phenotype link remains unresolved. SlrP, together with SspH1/SspH2, contributes redundantly to intracellular proliferation in fibroblasts. | Review + recent primary | Infection phenotypes in epithelial cells, dendritic cells, fibroblasts; review synthesis | Pillay et al. 2023 *Microbiology*; Bullones-Bolaños et al. 2024 *Frontiers in Immunology*; Worley 2025 *IJMS* | https://doi.org/10.1099/mic.0.001342; https://doi.org/10.3389/fimmu.2024.1328707; https://doi.org/10.3390/ijms26062611 | (pqac-00000001, pqac-00000002, pqac-00000011, pqac-00000014) |
| Quantitative/statistical notes | Salmonella encodes >40 effectors overall; one 2014 source notes at least 38 effectors categorized as 7 T3SS1-only, 22 T3SS2-only, and 9 secreted by both systems. Translocation/readouts in recent work were measured at 2, 4, and 8 h p.i.; competitive intracellular proliferation assays used a 10:1 input ratio, and only NRK fibroblasts showed a significant defect for the *slrP sspH1 sspH2* triple mutant, with smaller significant reductions for *slrP sspH1* and *slrP sspH2* double mutants. For SNRPD2, ubiquitinated lysines K85 and K92 were mapped, with Lys92 preferred but not exclusive. | Primary + review | cAMP translocation assays, competitive infection assays, mass spectrometry mapping | Cordero-Alba & Ramos-Morales 2014 *Journal of Bacteriology*; Bullones-Bolaños et al. 2022 *Biology*; Bullones-Bolaños et al. 2024 *Frontiers in Immunology*; Pillay et al. 2023 *Microbiology* | https://doi.org/10.1128/jb.02158-14; https://doi.org/10.3390/biology11101517; https://doi.org/10.3389/fimmu.2024.1328707; https://doi.org/10.1099/mic.0.001342 | (pqac-00000009, pqac-00000011, pqac-00000013, pqac-00000018, pqac-00000019) |


*Table: This table summarizes evidence-supported functional annotation for Salmonella Typhimurium SlrP, including identity, secretion, regulation, enzymatic activity, host targets, localization, and phenotypic roles. It is useful as a compact evidence map linking each annotation claim to specific recent reviews and primary studies.*