Abstract
Escherichia coli (ETEC) strain H10407 contains a GTPase virulence factor, LeoA, which is encoded on a pathogenicity island and has been shown to enhance toxin release, potentially through vesicle secretion. By sequence comparisons and X-ray structure determination we now identify LeoA as a bacterial dynamin-like protein (DLP). Proteins of the dynamin family remodel membranes and were once thought to be restricted to eukaryotes. In ETEC H10407 LeoA localises to the periplasm where it forms a punctate localisation pattern. Bioinformatic analyses of leoA and the two upstream genes leoB and leoC suggest that LeoA works in concert with a second dynamin-like protein, made up of LeoB and LeoC. Disruption of the leoAB genes leads to a reduction in secretion of periplasmic Tat-GFP and outer membrane OmpA. Our data suggest a role for LeoABC dynamin-like proteins in potentiating virulence through membrane vesicle associated toxin secretion.
Highlights
Members of the dynamin family are large GTPases that couple nucleotide hydrolysis to membrane remodelling [1,2]
Sequence alignments of LeoA with other dynamin family members (DFMs) including BDLP1 from N. punctiforme, YjdA from E. coli, and the eukaryotic mitofusin Fzo1, showed obvious conserved dynamin-like domains that include a predicted membrane-binding domain correctly positioned between the classical dynamin middle domain and GTPase effector domain (GED) (Figure 1B)
Since most bacterial dynamins identified to date are encoded in tandem [6] this was not completely unexpected, the arrangement of leoC and leoB is unusual in that a single, contiguous gene encoding a putative dynamin-like protein (DLP) has been split into two genes (Figure 1B, 1C and 1D)
Summary
Members of the dynamin family are large GTPases that couple nucleotide hydrolysis to membrane remodelling [1,2]. In addition to classical dynamins, the protein family comprises dynamin-like proteins (DLPs), such as dynamin-related protein 1 (DRP1) and mitofusins, which are involved in mitochondrial fission and fusion, respectively [2]. DFMs have been found exclusively within eukaryotic cells but reports of dynamin-like proteins in bacteria show the family is larger than previously thought [6,7]. The role of these proteins in bacteria is still largely unknown
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