Colicins U and Y inhibit growth of Escherichia coli strains via recognition of conserved OmpA extracellular loop 1

• Published in: International journal of medical microbiology 2016-11, Vol.306 (7), p.486-494
• Main Authors: Bosák, Juraj, Micenková, Lenka, Doležalová, Magda, Šmajs, David
• Format: Article
• Language: English
• Subjects: Bacterial Outer Membrane Proteins - genetics; Bacterial Outer Membrane Proteins - metabolism; Colicin U; Colicin Y; Colicin-receptor interaction; Colicins - metabolism; DNA Mutational Analysis; Escherichia coli; Escherichia coli - drug effects; Escherichia coli - genetics; Escherichia coli - growth & development; Female; Humans; Infectious Disease; Male; Medical Education; Microbial Sensitivity Tests; OmpA; Protein Binding; Serratia marcescens - genetics
• ISSN: 1438-4221; 1618-0607
• DOI: 10.1016/j.ijmm.2016.07.002

Abstract Interactions of colicins U and Y with the OmpA (Outer membrane protein A) receptor molecule were studied using site-directed mutagenesis and colicin binding assay. A systematic mutagenesis of the colicin-susceptible OmpA sequence from Escherichia coli (OmpAEC ) to the colicin-resistant OmpA sequence from Serratia marcescens (OmpASM ) was performed in regions corresponding to extracellular OmpA loops 1–4. Susceptibility to colicins U and Y was significantly affected by the OmpA mutation in loop 1. As with functional analysis, a decrease in binding capacity of His-tagged colicin U was found for recombinant OmpA with a mutated segment in loop 1 compared to control OmpAEC . To verify the importance of the identified amino acid residues in OmpA loop 1, we introduced loop 1 from OmpAEC into OmpASM , which resulted in the substantial increase of susceptibility to colicins U and Y. In addition, colicins U and Y were tested against a panel of 118 bacteriocin non-producing strains of four Escherichia species, including E. coli (39 strains), E. fergusonii (10 strains), E. hermannii (42 strains), and E. vulneris (27 strains). A majority (82%) of E. coli strains was susceptible to colicins U and Y. Interestingly, colicins U and Y also inhibited all of the 30 tested multidrug-resistant E. coli O25b-ST131 isolates. These findings, together with the fact that OmpA loop 1 is important for bacterial virulence and is evolutionary conserved, offer the potential of using colicins U and Y as specific anti-OmpA loop 1 directed antibacterial proteins.