Proteomics analysis reveals that CirA in Aeromonas hydrophila is involved in nutrient uptake

The colicin I receptor (CirA) is a well-studied outer membrane protein that has been reported to play important roles in antibiotic resistance, virulence, and iron homeostasis, although its exact physiological roles require further investigation. In this study, differentially expressed proteins between the delta ahcirA and wild-type (WT) strains of Aeromonas hydrophila were compared using quantitative proteomics. Bioinformatics analysis revealed that the expression of peptide, histidine, and arginine ATP-binding cassette (ABC) transporter system-related proteins was significantly higher in the delta ahcirA strain. Subsequent growth assays revealed that delta ahcirA grew slower than the WT strain in nutrient-limited medium when supplemented with dipeptide, histidine, and arginine as the carbon source. Far-western blot analysis further confirmed that AhCirA can directly bind to histidine/ arginine and dipeptide small-molecule substrates in addition to their periplasmic-binding proteins, AhDppA and AhHisJ, respectively. These results indicate that AhCirA may play an important role in the uptake of amino acids and peptides as a channel-forming porin while also directly interacting with ABC transporters to transport nutrient substances into the plasma membrane. Overall, this study demonstrates that AhCirA is a multi-functional protein in A. hydrophila and extends our understanding of known nutrient transport mechanisms among bacteria.

Automated summary

This study used quantitative proteomics to compare differentially expressed proteins between the delta ahcirA and wild-type strains of Aeromonas hydrophila. Bioinformatics analysis showed that the expression of peptide, histidine, and arginine ATP-binding cassette (ABC) transporter system-related proteins was significantly higher in the delta ahcirA strain. Further experiments revealed that delta ahcirA grew slower than the wild-type strain in nutrient-limited medium supplemented with dipeptide, histidine, and arginine. Far-western blot analysis confirmed that AhCirA can directly bind to histidine/arginine and dipeptide small-molecule substrates. These findings suggest that AhCirA plays a role in amino acid and peptide uptake as a channel-forming porin and interacts with ABC transporters to transport nutrient substances.