Peculiarities of Primary MARTX Cytotoxin Structure in Non-Toxigenic Vibrio cholerae strains of Different serogroups

Abstract

Objective of the investigation was a comparative bioinformatics analysis of rtxA gene translation products  of Vibrio  cholerae strains  isolated  from  patients  and  environmental  objects. Materials and methods. 32 Vibrio cholerae strains from the Rostov-on-Don Research Anti-Plague Institute collection were used. DNA sequencing was conducted  on  the  MiSeq  platform  (Illumina),  gene  identification  and  analysis  was  carried  out  by  means  of  BioEdit 7.2.5, BLASTN 2.2.29, Blastp, Vector NTI Advance 11 software programs. Results and conclusions. The rtxA genes of the studied strains were represented by multiple alleles. AlignX-analysis of their deduced products divided 32 proteins into 3 separate clusters. The first one included proteins of O1 and nonO1/nonO139 strains similar to the prototype, the second – nonO1/nonO139 only, the third – O139. Blastp-analysis revealed that the proteins of the first cluster retained all  domains  characteristic  of  MARTX  – ACD  (actin  cross-linking),  RID  (Rho  GTFase  inactivation),  CPD  (cysteine protease) and ABH (alpha-beta hydrolase) which evidences the probability of manifestation of the typical activity. In 3 strains a new Hia domain (of putative adaptation factor) was detected. The proteins of the second cluster lacked ACD but formed an additional RID; two of which lacked ABH too, but in one, VIP2 domain (of actin modification) appeared and in another – Hia. These data are in accordance with the presumption of J. Dolores, K.J.F. Satchell (2013) on the possible converting of actinomodulator MARTX into toxins with other mechanisms of action. The proteins of O139 vibrios shared all specific domains except from ACD. For a number of altered proteins revealed by us full homologues were found in NCBI gene bank, belonging to isolates from other regions of the world. The presence of similar determinants in the genomes of strains of different origin points to non-occasional character of their conservation. It is possible that certain strains “deliberately” alter those genes or switch off the synthesis of the high-molecular toxin completely with a view to energy-saving.