Modular Structure of Microcin H47 and Colicin V

Abstract

Microcins are gene-encoded peptide antibiotics produced by enterobacteria that act on strains of gramnegative bacteria. In this work, we concentrated on higher-molecular-mass microcins, i.e., those possessing 60 or more amino acids. They can be subdivided into unmodified and posttranslationally modified peptides. In both cases, they exhibit conserved C-terminal sequences that appear to be characteristic of each subgroup. In the hypothesis that these sequences could correspond to domains, gene fusions between the activity genes for the unmodified microcin colicin V and the modified microcin H47 were constructed. These two microcins differ in their mode of synthesis, uptake, target, and specific immunity. Through this experimental approach, chimeric peptides with exchanged C-terminal sequences were encoded. Cells carrying the fusions in different genetic contexts were then assayed for antibiotic production. Many of them produced antibiotic activities with recombinant properties: the toxicity of one microcin and the mode of uptake of the other. The results led to the identification of a modular structure of colicin V and microcin H47, with the recognition of two domains in their peptide chains: a toxic N-terminal domain and an uptake C-terminal domain. This modular design would be shared by other microcins from each subgroup.

Mechanism of Bactericidal Activity of Microcin L inEscherichia coliandSalmonella enterica

“…We hypothesize that the MccL N-terminal sequence, which is quite different from the MccV one, is responsible for its specific antibiotic activity. This is in accordance with Azpiroz and Laviña (2), who showed that the specific toxicity of MccV and MccH47 was conferred by their N-terminal portions.…”

“…It was determined that a C-terminal domain of microcins E492, H47, and M was essential for the specific binding to FepA, Fiu, and Cir and possibly also for TonB-mediated import in the periplasm (4). Moreover, Azpiroz and Laviña (2) constructed chimeric peptides with exchanged C-terminal se- (57). However, we also observed that the exbB tolQ double mutant was not fully resistant to MccL, which suggests that another, unknown interaction and/or complementation exists.…”

pMPES: A Modular Peptide Expression System for the Delivery of Antimicrobial Peptides to the Site of Gastrointestinal Infections Using Probiotics

“…In another study, chimeras of MccV and Microcin H47 (MccH47) were shown to be secreted from the MccH47 secretion machinery using either the MccV or MccH47 signal peptides [51]. It was believed that this capability was due to the similarity in transport proteins.…”

A new hybrid bacteriocin, Ent35–MccV, displays antimicrobial activity against pathogenic Gram‐positive and Gram‐negative bacteria

“…On the other hand, Azpiroz and Laviña constructed hybrid microcins fusing the N‐ and C‐terminal domains of MccV and MccH47. They arrived to the conclusion that the C‐terminal domains of these class II microcins are involved in the recognition of the OM receptor for the target cell uptake and the N‐terminal domain is the toxic region of the molecule [33]. Both, class IIa of LAB bacteriocin and class II of microcins must have an IM receptor binding region.…”