Investigating the Oligomeric State of Osmoregulatory Transporter ProP of Escherichia coli and its Functional Consequences

Abstract

ProP, an osmoregulatory transporter found in E. coli, is responsible for the accumulation of osmolytes in response to hyperosmotic stress. ProP is able to dimerize through the formation of a C-terminal coiled coil and the oligomeric state of ProP may play a role in ProP function. The effects of detergents, particularly n-dodecyl-β-D-maltoside, on the oligomeric state of ProP were studied using blue native polyacrylamide gel electrophoresis and laser induced liquid bead ion desorption mass spectrometry. These techniques showed that ProP is primarily monomeric in vitro, implying that ProP studied in proteoliposomes may also exist, at least in part, as a monomer. The functional significance of ProP dimerization was probed by attempting to observe a dominant negative effect in vivo. In vivo work suggested that ProP may not require dimerization to be active and future work will use the same approach to probe the role of dimerization in vitro.