6533b7d1fe1ef96bd125cc57

RESEARCH PRODUCT

Domain organization and evolution of multifunctional autoprocessing repeats-in-toxin (MARTX) toxin in Vibrio vulnificus.

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ABSTRACT The objective of this study was to analyze multifunctional autoprocessing repeats-in-toxin (MARTX) toxin domain organization within the aquatic species Vibrio vulnificus as well as to study the evolution of the rtxA1 gene. The species is subdivided into three biotypes that differ in host range and geographical distribution. We have found three different types (I, II, and III) of V. vulnificus MARTX (MARTX Vv ) toxins with common domains (an autocatalytic cysteine protease domain [CPD], an α / β-hydrolase domain, and a domain resembling that of the LifA protein of Escherichia coli O127:H6 E2348/69 [Efa/LifA]) and specific domains (a Rho-GTPase inactivation domain [RID], a domain of unknown function [DUF],a domain resembling that of the rtxA protein of Photorhabdus asymbiotica [ rtxA PA ], and an actin cross-linking domain [ACD]). Biotype 1 isolates harbor MARTX Vv toxin types I and II, biotype 2 isolates carry MARTX Vv toxin type III, and biotype 3 isolates have MARTX Vv toxin type II. The analyzed biotype 2 isolates harbor two identical copies of rtxA1 , one chromosomal and the other plasmidic. The evolutionary history of the gene demonstrates that MARTX Vv toxins are mosaics, comprising pieces with different evolutionary histories, some of which have been acquired by intra- or interspecific horizontal gene transfer. Finally, we have found evidence that the evolutionary history of the rtxA1 gene for biotype 2 differs totally from the gene history of biotypes 1 and 3.