Inner membrane proteins YgdD and SbmA are required for the complete susceptibility of escherichia coli to the proline-rich antimicrobial peptide arasin 1(1\u201325)

Arasin 1 from the spider crab Hyas araneus is a proline-rich antimicrobial peptide (PR-AMP), which kills target bacteria by a non-membranolytic mechanism. By using a fluorescent derivative of the peptide, we showed that arasin 1 rapidly penetrates into Escherichia coli cells without membrane damage. To unravel its mode of action, a knockout gene library of E. coli was screened and two types of mutants with a less susceptible phenotype to the arasin 1 fragment (1\u201323) were found. The first bore the mutation of sbmA, a gene coding for an inner membrane protein involved in the uptake of different antibiotic peptides. The second mutation was located in the ygdD gene, coding for a conserved inner membrane protein of unknown function. Functional studies showed that YgdD is required for the full susceptibility to arasin 1(1\u201325), possibly by supporting its uptake and/or intracellular action. These results indicated that different bacterial proteins are exploited by arasin 1(1\u201325) to exert its antibacterial activity and add new insights on the complex mode of action of PR-AMP