Dicarboxylic acid transport in Escherichia coli K12: involvement of a binding protein in the translocation of dicarboxylic acids across the outer membrane of the cell envelope

Abstract

The dicarboxylate transport system in E. coli K12 is an active transport system. At least 1 binding protein and 2 cytoplasmic membrane transport components are involved in the uptake of dicarboxylic acids. Surface labeling studies showed that some dicarboxylate binding proteins were exposed on the cell surface. The dicarboxylate transport component located in the outer membrane can be inactivated by 2 different kinds of nonpenetrating inhibitors, i.e., proteases, and diazosulfanilic acid. These inhibitors seem to act on the dicarboxylate binding protein. By adding this protein to inactivated cells or to transport-negative mutants, the dicarboxylate transport system is reconstituted. The dicarboxylate binding protein found on the cell surface plays an essential role in the translocation of dicarboxylic acids across the outer membrane.