EvfB or VasL is a domain found on many Gram-negative proteins with an ImpA_N domain at the N-terminus. These proteins are expressed from the pathogenicity locus that forms the bacterial type VI secretion system. The exact function of VasL is not known. One E.coli member is annotated as being EvfB, though the E.coli equivalent of ImpA would be expected to be EvfG. It is possible that in many bacteria what is a single protein in one species, eg E.coli, is a fusion of two genes in others, which would explain an ImpA at the N-terminus and a VasL at the C-terminus.