Polymorphic toxin systems: Comprehensive characterization of trafficking modes, processing, mechanisms of action, immunity and ecology using comparative genomics.
-
Imm35 (PF15567) was identified as an immunity protein family in bacterial polymorphic toxin systems, specifically associated with the papain-like peptidase Tox-PL1 toxin domain.
"Imm35 is specifically associated only with the papain-like peptide Tox-PL1, suggesting that it functions specifically as a peptidase inhibitor"
-
Over 90 families of immunity proteins were identified in polymorphic toxin systems, neutralizing between one and at least 27 distinct types of toxin domains.
"Over 90 families of immunity proteins might neutralize anywhere between a single to at least 27 distinct types of toxin domains"
YrhB is a highly stable small protein with unique chaperone-like activity in Escherichia coli BL21(DE3).
-
YrhB from E. coli BL21(DE3) showed chaperone-like activity: it prevented heat-induced aggregation of PurK, promoted in vitro refolding of uridine phosphorylase, and reduced inclusion body formation. YrhB was upregulated only under heat shock. However, this was demonstrated in BL21(DE3), not K12.
"Escherichia coli YrhB (10.6 kDa) from strain BL21(DE3) that is commonly used for protein overexpression is a stable chaperone-like protein and indispensable for supporting the growth of BL21(DE3) at 48 °C but not defined as conventional heat shock protein (HSP)"
Identification and characterization of Zn(II)-responsive genes and proteins in E. coli.
-
yrhB (b3446) is upregulated 4.3-fold (P=2.75e-02) under TPEN (zinc chelation) stress after 30 minutes, suggesting a possible link to metal homeostasis or stress response.
"yrhB b3446 up-regulated under TPEN stress with mean fold change 4.3 and P = 2.75e-02"
Limitations of current machine learning models in predicting enzymatic functions for uncharacterized proteins.
-
DeepECTF incorrectly predicted EC 4.1.2.50 (6-carboxytetrahydropterin synthase) for YrhB. This is a logic error because E. coli already encodes this enzyme as QueD (b2765), and a queD mutant lacks the activity entirely.
"YrhB/b3446 is predicted to be a 6-carboxytetrahydropterin synthase (EC 4.1.2.50), but E. coli already encodes this enzyme (QueD/b2765) and a queD mutant lacks this activity (Zallot et al. 2017)"
-
This exemplifies how ML models can ignore existing gene-function assignments in the organism, leading to logically impossible predictions.
"current ML methods not only mostly fail to make novel predictions but also make basic logic errors in their predictions that human annotators avoid by leveraging the available knowledge base"
The complete genome sequence of Escherichia coli K-12.
-
yrhB (b3446) was identified in the E. coli K12 genome sequencing.
"Of 4288 protein-coding genes annotated, 38 percent have no attributed function"
OpenScientist hypothesis run: YrhB Imm35 fold vs function (immunity / peptidase-inhibitor over-annotation)
-
Compute-driven analysis confirmed the Imm35 fold (AlphaFold pLDDT 95.2, Foldseek) but found the ISS immunity / peptidase-inhibitor annotations over-annotated (no Imm35 member has experimental immunity evidence; no adjacent toxin gene in K12). Recommends GO:0044183 (protein folding chaperone) + GO:0042026 (protein refolding) with IDA from PMID:22569261, since K12 and BL21(DE3) YrhB are 100% identical.
"YrhB functions as a chaperone-like protein with multiple validated activities, using a protein 100% identical between the BL21(DE3) strain used in the study and the K12 reference strain."