Truncation of MalF Results in Lactose Transport via the Maltose Transport System of Escherichia coli

Merino, Gonzalo; Shuman, Howard A.

doi:10.1074/jbc.273.4.2435

Cited by 9 publications

(7 citation statements)

References 43 publications

(19 reference statements)

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“…Discontinuous hydrophilic patches involved in substrate translocation may indicate a low specificity of the channel. This hypothesis is supported by recent findings in which the maltose transporter can transport lactose when MalF was either truncated or altered by a point mutation (Merino and Shuman, 1997; 1998).…”

Section: Possible Mechanisms Of Substrate Translocation Across the Cysupporting

confidence: 69%

The ABC maltose transporter

Ehrmann

Ehrle

Hofmann

et al. 1998

Molecular Microbiology

115

104

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SummaryBacterial ATP-binding cassette (ABC) transporters and their homologues in eukaryotic cells form one of the largest superfamilies known today. They function as primary pumps that couple substrate translocation across the cytoplasmic membrane to ATP hydrolysis. Although ABC transporters have been studied for more than three decades, the structure of these multicomponent systems is unknown, and the mechanism of transport is not understood. This article reviews one of the most widely studied ABC systems, the maltose transporter of Escherichia coli. A first structural model of the transport channel allows discussion of possible mechanisms of transport. In addition, recent experimental evidence suggests that regulation of gene expression and transport activity is far more complex than expected. History and general properties

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Section: Possible Mechanisms Of Substrate Translocation Across the Cysupporting

confidence: 69%

The ABC maltose transporter

Ehrmann

Ehrle

Hofmann

et al. 1998

Molecular Microbiology

115

104

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show abstract

“…Random and site-directed mutagenesis of the membrane-spanning domains of the maltose transporter has generated mutants with altered specificities (137,464,475,517), some of which transport maltose but not maltodextrins and vice versa. In one of the most remarkable alterations in substrate specificity, an amber mutation that led to the premature termination of the TM protein MalF permitted growth of genotypically Lac-negative cells on lactose (313). Transport required maltose-BP, though lactose is not bound by maltose-BP, suggesting that the truncation allowed access of lactose to the TM translocation pathway.…”

Section: Bpd Uptake Systemsmentioning

confidence: 99%

Structure, Function, and Evolution of Bacterial ATP-Binding Cassette Systems

Davidson

Dassa

Orelle

et al. 2008

Microbiol Mol Biol Rev

1,187

1,137

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SUMMARY ATP-binding cassette (ABC) systems are universally distributed among living organisms and function in many different aspects of bacterial physiology. ABC transporters are best known for their role in the import of essential nutrients and the export of toxic molecules, but they can also mediate the transport of many other physiological substrates. In a classical transport reaction, two highly conserved ATP-binding domains or subunits couple the binding/hydrolysis of ATP to the translocation of particular substrates across the membrane, through interactions with membrane-spanning domains of the transporter. Variations on this basic theme involve soluble ABC ATP-binding proteins that couple ATP hydrolysis to nontransport processes, such as DNA repair and gene expression regulation. Insights into the structure, function, and mechanism of action of bacterial ABC proteins are reported, based on phylogenetic comparisons as well as classic biochemical and genetic approaches. The availability of an increasing number of high-resolution structures has provided a valuable framework for interpretation of recent studies, and realistic models have been proposed to explain how these fascinating molecular machines use complex dynamic processes to fulfill their numerous biological functions. These advances are also important for elucidating the mechanism of action of eukaryotic ABC proteins, because functional defects in many of them are responsible for severe human inherited diseases.

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“…MalF, a maltose primary active transporter, was found upon mutation to accommodate lactose as a substrate (Merino & Shuman, 1998). To our knowledge, however, a naturally occurring MFS secondary active transport system for maltose has not been experimentally characterized in bacteria; we report here that CscB may be the first such bacterial maltose secondary transporter system, as other maltose transport systems found so far are in eukaryotes, such as MAL6T (Saier et al, 1999; Yao, Sollitti & Marmur, 1989), and maltose transport has not been definitively demonstrated by MaltP of Bacillus halodurans (Takami et al, 2000).…”

Section: Resultsmentioning

confidence: 99%

Evidence for the Transport of Maltose by the Sucrose Permease, CscB, of Escherichia coli

et al. 2009

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The purpose of this study was to examine the sugar recognition and transport properties of the sucrose permease (CscB), a secondary active transporter from Escherichia coli. We tested the hypothesis that maltose transport is conferred by the wild-type CscB transporter. Cells of E. coli HS4006 harboring pSP72/cscB were red on maltose MacConkey agar indicator plates. We were able to measure "downhill" maltose transport and establish definitive kinetic behavior for maltose entry in such cells. Maltose was an effective competitor of sucrose transport in cells with CscB, suggesting that the respective maltose and sucrose binding sites and translocation pathways through the CscB channel overlap. Accumulation ("uphill" transport) of maltose by cells with CscB was profound, demonstrating active transport of maltose by CscB. Sequencing of cscB encoded on plasmid pSP72/ cscB used in cells for transport studies indicate an unaltered primary CscB structure, ruling out the possibility that mutation conferred maltose transport by CscB. We conclude that maltose is a bona fide substrate for the sucrose permease of E. coli. Thus, future studies of sugar binding, transport and permease structure should consider maltose, as well as sucrose.

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Truncation of MalF Results in Lactose Transport via the Maltose Transport System of Escherichia coli

Cited by 9 publications

References 43 publications

The ABC maltose transporter

The ABC maltose transporter

Structure, Function, and Evolution of Bacterial ATP-Binding Cassette Systems

Evidence for the Transport of Maltose by the Sucrose Permease, CscB, of Escherichia coli

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