Journal: Journal of Structural Biology: X

Article Title: Salt bridge disruption in colicin Ib channel-forming domain enhances membrane translocation and bactericidal activity

doi: 10.1016/j.yjsbx.2026.100144

Figure Lengend Snippet: E. coli viability after the treatments of full-length ColIb and salt bridge variants using spot assay and CFU analysis. E. coli ATCC8739 treated with full-length WT ColIb or salt bridge variants, in the a, c absence and b, d presence of the iron chelator, 2,2′ bipyridine (100 μM), were 10-fold serially diluted and spotted. The groups treated with the protein buffer were included as a negative control. The bacterial cell viabilities treated with 0.1 nM and 0.01 nM of protein samples are compared in b . Data represent the mean ± S.D. with n = 3 independent experimental replicates. Statistical analyses were assessed using a one-way ANOVA in GraphPad Prism. * p ≤ 0.05, ** p ≤ 0.01, *** p ≤ 0.001, **** p ≤ 0.0001, n.s., not significant.

Article Snippet: Since the above experimental results demonstrated that disrupting the electrostatic interactions in the C-domain leads to a more loosely packed tertiary structure, which may reduce the unfolding energy required for translocation through CirA and facilitate membrane insertion, we sought to characterize the antibacterial activity by monitoring the viability of E. coli ATCC 8739 treated with full-length ColIb and its salt bridge variants ( , ).

Techniques: Spot Test, Negative Control

Journal: Journal of Structural Biology: X

Article Title: Salt bridge disruption in colicin Ib channel-forming domain enhances membrane translocation and bactericidal activity

doi: 10.1016/j.yjsbx.2026.100144

Figure Lengend Snippet: Bactericidal activity of the WT ColIb C-domain and salt bridge variants using the spot-on-lawn antimicrobial assay. Three-fold serially diluted a , b isolated ColIb C-domain and variants, and c , d full-length ColIb were spotted on the lawn of E. coli ATCC8739. The WT ColIb C-domain and variants were purified at pH 6.0 ( a , b left) and pH 4.5 ( a , b right) for spotting. The C-domain-truncated ColIb variant (TR) was pre-spotted on the plate before spotting b the ColIb C-domain and variants, and d full-length ColIb. Refer to Methods for details.

Article Snippet: Since the above experimental results demonstrated that disrupting the electrostatic interactions in the C-domain leads to a more loosely packed tertiary structure, which may reduce the unfolding energy required for translocation through CirA and facilitate membrane insertion, we sought to characterize the antibacterial activity by monitoring the viability of E. coli ATCC 8739 treated with full-length ColIb and its salt bridge variants ( , ).

Techniques: Activity Assay, Isolation, Purification, Variant Assay