Phylogenetic analysis of T6SSs lead to the classification of the F. tularensis T6SS as a unique subtype T6SSii. Representatives of T6SSi are widespread among Proteobacteria, whereas T6SSiii have so far been identified only in Bacteroidetes. Out of the 13 proteins that define the core of prototypical T6SSs, the FPI lacks obvious homologues for at least 5 of them. A TssM/IcmF family protein (PdpB) lacks the conserved Walker A box required to bind ATP and to provide energy to the secretion process. Francisella VgrG protein is much smaller than prototypical VgrG proteins. The atypical T6SS might be linked to its unique ability to target the eukaryotic phagosomal membrane. ...
Phylogenetic analysis of T6SSs lead to the classification of the F. tularensis T6SS as a unique subtype T6SSii. Representatives of T6SSi are widespread among Proteobacteria, whereas T6SSiii have so far been identified only in Bacteroidetes. Out of the 13 proteins that define the core of prototypical T6SSs, the FPI lacks obvious homologues for at least 5 of them. A TssM/IcmF family protein (PdpB) lacks the conserved Walker A box required to bind ATP and to provide energy to the secretion process. Francisella VgrG protein is much smaller than prototypical VgrG proteins. The atypical T6SS might be linked to its unique ability to target the eukaryotic phagosomal membrane. ...
Phylogenetic analysis of T6SSs lead to the classification of the F. tularensis T6SS as a unique subtype T6SSii. Representatives of T6SSi are widespread among Proteobacteria, whereas T6SSiii have so far been identified only in Bacteroidetes. Out of the 13 proteins that define the core of prototypical T6SSs, the FPI lacks obvious homologues for at least 5 of them. A TssM/IcmF family protein (PdpB) lacks the conserved Walker A box required to bind ATP and to provide energy to the secretion process. Francisella VgrG protein is much smaller than prototypical VgrG proteins. The atypical T6SS might be linked to its unique ability to target the eukaryotic phagosomal membrane. ...