Microcin E492, a bacteriocin from "Klebsiella pneumoniae" : amyloid formation and mode of action

La microcine E492 (MccE492) est une protéine sécrétée par "Klebsiella pneumoniae" qui tue diverses entérobactéries en causant une dépolarisation et une perméabilisation de la membrane cytoplasmique. Nous montrons que MccE492 forme "in vitro" et "in vivo" des fibres amyloïdes qui ont les mêmes propriétés que celles des amyloïdoses, formées par des protéines d'organismes eucaryotes. La formation de fibres amyloïdes correspond à une perte de l'activité de MccE492. Alors que plusieurs protéines spécifiques sont nécessaires pour la production de MccE492 extracellulaire active, l'expression intracellulaire d'uniquement MceA, la protéine structurale de Mcc492, est toxique. Cette toxicité est augmentée par le ciblage de MceA vers la membrane interne. Le domaine C-terminal de MccE492 est seulement nécessaire pour son import vers le périplasme, et non pas pour endommager la membrane interne. Enfin, la toxicité de MccE492 dépend de son association avec ManYZ, la mannose peméase de la membrane interne

The polypeptide core of Microcin E492 stably associates with the mannose permease and interferes with mannose metabolism

Microcin E492 (MccE492) is an antibacterial protein whose activity on target cells requires ManYZ, the inner membrane component of the mannose permease. We show here that MceA, the polypeptide core of MccE492, stably associates with ManYZ both in the presence and in the absence of MceB, the MccE492 immunity protein. The two known physiological activities of the mannose permease were assayed in cells co-expressing MceA and MceB. Under these conditions, growth on mannose as the sole carbon source is prevented; this was not observed in cells expressing only MceB. In contrast, susceptibility to bacteriophage λ infection was not affected

Bactericidal Activity of both Secreted and Nonsecreted Microcin E492 Requires the Mannose Permease

Microcin E492 (MccE492) is a bactericidal protein secreted by Klebsiella pneumoniae that is active against various species of Enterobacteriaceae. Interaction of MccE492 with target cells leads to the depolarization and permeabilization of their inner membranes. Several MccE492-specific proteins are required for the maturation and secretion of active MccE492. Surprisingly, the expression of only MceA, the polypeptide backbone of MccE492, is shown here to be toxic by itself. We refer to this phenomenon as endogenous MceA bactericidal activity to differentiate it from the action of extracellularly secreted MccE492. The toxicity of endogenous MceA is enhanced by an efficient targeting to the inner membrane. However, a periplasmic intermediate state is not required for MceA toxicity. Indeed, endogenous MceA remains fully active when it is fused to thioredoxin-1, a fast-folding protein that promotes retention of the C terminus of MceA in the cytoplasm. The C-terminal domain of MccE492 is required only for delivery from the extracellular environment to the periplasm, and it is not required for inner membrane damage. A common component is absolutely essential for the bactericidal activity of both endogenous MceA and extracellular MccE492. Indeed, toxicity is strictly dependent on the presence of ManYZ, an inner membrane protein complex involved in mannose uptake. Based on these findings, we propose a new model for cell entry, inner membrane insertion, and toxic activity of MccE492

The management structure of FIND.

<p>Diagnostic programmes for various diseases operate as independent business units, supported by expertise that cuts across the programmes. SAC: scientific advisory committee, CSO: chief scientific officer, STO: senior technology officer, CFO: chief finance officer, SOO: senior operations officer, SPO: senior policy officer.</p

The result of a LAMP test is determined by visual inspection of reaction tubes.

<p>Positive samples exhibit bright green fluorescence (right) and are thus easily distinguished from negative ones (left) (<i>courtesy of Eiken Chemical</i>).</p

Reducing malnutrition through education actions

Non-PRIFPRI5PHN

Amyloid formation modulates the biological activity of a bacterial protein

The aggregation of proteins into amyloid fibrils is the hallmark feature of a group of late-onset degenerative diseases including Alzheimer, Parkinson, and prion diseases. We report here that microcin E492, a peptide naturally produced by Klebsiella pneumoniae that kills bacteria by forming pores in the cytoplasmic membrane, assembles in vitro into amyloid-like fibrils. The fibrils have the same structural, morphological, tinctorial, and biochemical properties as the aggregates observed in the disease conditions. In addition, we found that amyloid formation also occurs in vivo where it is associated with a loss of toxicity of the protein. The finding that microcin E492 naturally exists both as functional toxic pores and as harmless fibrils suggests that protein aggregation into amyloid fibrils is an evolutionarily conserved property of proteins that can be successfully employed by bacteria to fulfill specific physiological needs