Inner membrane proteins YgdD and SbmA are required for the complete susceptibility of Escherichia coli to the proline-rich antimicrobial peptide arasin 1(1–25)

Abstract

Arasin 1 from the spider crab <i>Hyas araneus</i> 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 <i>Escherichia coli</i> cells without membrane damage. To unravel its mode of action, a knockout gene library of <i>E. coli</i> was screened and two types of mutants with a less susceptible phenotype to the arasin 1 fragment (1-23) were found. The first bore the mutation of <i>sbmA</i>, a gene coding for an inner membrane protein involved in the uptake of different antibiotic peptides. The second mutation was located in the <i>ygdD</i> 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(1-25), possibly by supporting its uptake and/or intracellular action. These results indicated that different bacterial proteins are exploited by arasin 1(1-25) to exert its antibacterial activity and add new insights on the complex mode of action of PR-AMPs.