9.B.83 The Possible Outer Membrane Secretory Protein LeoA (LeoA) Family

Enterotoxigenic Escherichia coli (ETEC) causes enterotoxin-induced diarrhoea and mortality. The molecular mechanisms underlying how the heat-labile enterotoxin (LT) is secreted during infection are poorly understood. ETEC produces outer-membrane vesicles (OMVs) containing LT that are endocytosed into host cells. Although OMV production and protein content may be a regulated component of ETEC pathogenesis, how LT loading into OMVs is regulated is unknown. The LeoA protein plays a role in secreting LT from the bacterial periplasm. LeoA hydrolyses GTP which is important to LeoA's function in LT secretion; it may play a modest role in the formation and protein content of OMVs. Deletion of LeoA reduced the abundance of OmpX in outer-membrane protein preparations and of LT in OMVs.

LeoA is an Era-like protein of the ABC-ATPase superfamily. It has GTP-binding and 'switch' domains that overlap with G1-G5 boxes. It is an HSR-1 related homologue that is called the labile enterotoxin output A protein.