MOMP, a divergent porin from Campylobacter: cloning and primary structural characterization

We report a structural analysis at the molecular level of MOMP from Campylobacter, a gram-negative bacteria responsible for diarrhea. The corresponding gene was cloned and sequenced. Sequence comparison of seven MOMP sequences (three extracted from protein databases and four determined in this study) from distinct strains indicated alternation of preserved and divergent regions. No other significant sequence similarities could be detected. Comparison of MOMP with the crystal structures of other porins strongly suggested that it might adopt a similar fold and revealed the conservation of the monomer-monomer interface. The conservation clustered in the regions comprising or interacting with the loop L2. On the contrary, strands not involved in the interface are more divergent. Proteolysis assays and biochemical treatment supported the proposed model. Our study suggested that MOMP belong to the maltoporin super-family sharing common structural motifs. In view of this model we discuss its specificity and its global stability.