Interspecific reconstitution of maltose transport and chemotaxis in Escherichia coli with maltose-binding protein from various enteric bacteria

Abstract

In Escherichia coli, the periplasmic maltose-binding protein (MBP), the product of the malE gene, is the primary recognition component of the transport system for maltose and maltodextrins. It is also the maltose chemoreceptor, in which capacity it interacts with the signal transducer Tar (taxis to aspartate and some repellents). In studies of the maltose system in other members of the family Enterobacteriaceae, we found that MBP is produced by Salmonella typhimurium, Klebsiella pneumoniae, Enterobacter aerogenes, and Serratia marcescens. MBP from all of these species cross-reacted with antibody against the E. coli protein and had a similar molecular weight (about 40,000). The Shigella flexneri and Proteus mirabilis strains we examined did not synthesize MBP. The isoelectric points of MBP from different species varied from the acid extreme of E. coli (4.8) to the basic extreme of E. aerogenes (8.9). All species with MBP transported maltose with high affinity, although the Vmax for K. pneumoniae was severalfold lower than that for the other species. Maltose chemotaxis was observed only in E. coli and E. aerogenes. In S. typhimurium LT2, Tar was completely inactive in maltose taxis, although it signaled normally in response to aspartate. MBP isolated from all five species could be used to reconstitute maltose transport and taxis in a delta malE strain of E. coli after permeabilization of the outer membrane with calcium.

Ligand-induced structural changes to maltodextrin-binding protein as studied by solution NMR spectroscopy

“…The NMR data indicates that ligand binding primarily involves changes in domain orientations, critical for interaction with the Tar and MalFGK 2 receptors. 5,6 Local structural changes mainly occur at the domain interface as indicated by chemical shift data. The invariance of intra-domain structure is further con®rmed by the residual DC data.…”

“…5 The MBP/maltodextrin complex can also act as a ligand for the Tar receptor. 6 Binding of MBP to the periplasmic domain of Tar leads to a signal transduction cascade in which CheA is dephosphorylated, 7 ultimately resulting in chemotaxis.…”

Maltodextrin-based imaging probes detect bacteria in vivo with high sensitivity and specificity

“…1). Maltohexaose is a major source of glucose for bacteria 16 and MDPs can therefore deliver millimolar concentrations of imaging probes into bacteria, making it possible to image low numbers of bacteria. MDPs also have high specificity for bacteria because mammalian cells do not express the maltodextrin transporter 9 and cannot internalize contrast agents conjugated to maltohexaose.…”

Maltose‐binding protein interacts simultaneously and asymmetrically with both subunits of the Tar chemoreceptor

“…E. coli Tar displays a stronger negative co-operativity for aspartate binding than does S. fyphimurium Tar (Biemann and Koshland, 1994). S. typhimurium Tar does not mediate responses to maltose (Dahl and Manson, 1985;Mizuno et a/., 1986), and so it is free to use the second, lower-affinity binding site generated by negative co-operativity to expand the range of aspartate concentrations to which it responds. As MBP interacts with Tar along a central axis of the dimer (Fig.…”