Functional Relevance of Unstructured Regions of AcrA, the Periplasmic Adaptor of the Major Multidrug Efflux System in E. coli

Abstract

Efflux pumps, combined with low permeability of the outer membrane of gram negative bacteria play a crucial role in bacteria multi‐drug resistance. There are five classes of efflux pumps but the major and most studied of the efflux system in E. coli is the resistance nodulation cell division (RND) pump. This pump is a complex of three proteins: the inner membrane transporter AcrB, the periplasmic adaptor AcrA, and the outer membrane protein channel TolC. Of the three proteins, the structure and dynamic behavior of AcrA remain to be fully elucidated. In this study the functional roles of the unstructured regions at the N‐ and C‐termini of the protein were examined. These structurally unresolved regions include residues 26–37 at the N‐terminus, and residues 376 to 397 at the C‐terminus. We conducted truncation mutation to systematically remove residues from the C‐terminus of AcrA, and found that residues after Q376 are indeed not functionally important. The truncated AcrA, in which E377 is replaced by a stop codon, is fully active. On the N‐terminus, we created a mutant in which four amino acid residues (Q31QGG34) were deleted. The mutant was nonfunctional. To understand the mechanism of function disruption, we modified the membrane anchoring of AcrA, and determined the role of these first 13 residues at the N‐terminus of the mature AcrA sequence.Support or Funding InformationNSF grant CHE‐1709381This abstract is from the Experimental Biology 2019 Meeting. There is no full text article associated with this abstract published in The FASEB Journal.