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3.A.1.1.1
Maltooligosaccharide porter. The 3-D structure has been reported by Oldham et al. (2007). An altering access mechanism has been suggested for the maltose transporter resulting from rigid-body rotations (Khare et al., 2009). The maltose-binding protein is open in the catalytic transition state for ATP hydrolysis during maltose transport (Austermuhle et al. 2004). Bordignon et al. (2010) and Schneider et al. (2012) reviewed the extensive knowledge available on MalEFGK2, its mode of action and its regulatory interactions.  The transporter sequesters the MalT transcriptional activator at the cytoplasmic surface of the membrane in the absence of the transport substrate (Richet et al. 2012).  The crystal structures of the transporter complex MBP-MalFGK2 bound with large malto-oligosaccharide in two different conformational states have also been determined. In the pretranslocation structure, Oldham et al. 2013 found that the transmembrane subunit MalG forms two hydrogen bonds with malto-oligosaccharide at the reducing end. In the outward-facing conformation, the transmrembrane subunit MalF binds three glucosyl units from the nonreducing end. These structural features explain why large modified malto-oligosaccharides are not transported by MalFGK2 despite their high binding affinity to MBP. In the transport cycle, substrate is channeled from MBP into the transmembrane pathway with a polarity such that both MBP and MalFGK2 contribute to the overall substrate selectivity of the system (Oldham et al. 2013).  Stabilization of the semi-open MalK2 conformation by maltose-bound MBP is key to the coupling of maltose transport to ATP hydrolysis in vivo, because it facilitates the progression of the MalK dimer from the open to the semi-open conformation, from which it can proceed to hydrolyze ATP (Alvarez et al. 2015). Both the binding of MalE to the periplasmic side of the transmembrane complex and binding of ATP to MalK2 are necessary to facilitate the conformational change from the inward-facing state to the occluded state, in which MalK2 is completely dimerized (Hsu et al. 2017). An integrated transport mechanism of the maltose ABC importer has been proposed (Mächtel et al. 2019).

Accession Number:P0AEX9
Protein Name:Maltose-binding periplasmic protein MalE aka B4034
Length:396
Molecular Weight:43388.00
Species:Escherichia coli [83333]
Number of TMSs:1
Location1 / Topology2 / Orientation3: Periplasm1
Substrate Maltooligosaccharides, Maltose

Cross database links:

DIP: DIP-31871N
RefSeq: AP_004535.1    NP_418458.1   
Entrez Gene ID: 948538   
Pfam: PF01547   
BioCyc: EcoCyc:MALE-MONOMER    ECOL168927:B4034-MONOMER   
KEGG: ecj:JW3994    eco:b4034   

Gene Ontology

GO:0055052 C:ATP-binding cassette (ABC) transporter comp...
GO:0042597 C:periplasmic space
GO:0048030 F:disaccharide binding
GO:0005363 F:maltose transmembrane transporter activity
GO:0042956 P:maltodextrin transport
GO:0015768 P:maltose transport

References (12)

[1] “Sequences of the malE gene and of its product, the maltose-binding protein of Escherichia coli K12.”  Duplay P.et.al.   6088507
[2] “Analysis of the Escherichia coli genome. IV. DNA sequence of the region from 89.2 to 92.8 minutes.”  Blattner F.R.et.al.   8265357
[3] “The complete genome sequence of Escherichia coli K-12.”  Blattner F.R.et.al.   9278503
[4] “Highly accurate genome sequences of Escherichia coli K-12 strains MG1655 and W3110.”  Hayashi K.et.al.   16738553
[5] “A DNA sequence containing the control regions of the malEFG and malK-lamB operons in Escherichia coli K12.”  Bedouelle H.et.al.   6283312
[6] “Promoters of the malEFG and malK-lamB operons in Escherichia coli K12.”  Bedouelle H.et.al.   6185687
[7] “The nucleotide sequence of the gene for malF protein, an inner membrane component of the maltose transport system of Escherichia coli. Repeated DNA sequences are found in the malE-malF intercistronic region.”  Froshauer S.et.al.   6088520
[8] “Comparing the predicted and observed properties of proteins encoded in the genome of Escherichia coli K-12.”  Link A.J.et.al.   9298646
[9] “Protein identification with N and C-terminal sequence tags in proteome projects.”  Wilkins M.R.et.al.   9600841
[10] “The 2.3-A resolution structure of the maltose-or maltodextrin-binding protein, a primary receptor of bacterial active transport and chemotaxis.”  Spurlino J.C.et.al.   2002054
[11] “Crystallographic evidence of a large ligand-induced hinge-twist motion between the two domains of the maltodextrin binding protein involved in active transport and chemotaxis.”  Sharff A.J.et.al.   1420181
[12] “Extensive features of tight oligosaccharide binding revealed in high-resolution structures of the maltodextrin transport/chemosensory receptor.”  Quiocho F.A.et.al.   9309217
Structure:
1A7L   1ANF   1DMB   1EZ9   1EZO   1EZP   1FQA   1FQB   1FQC   1FQD   [...more]

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FASTA formatted sequence
1:	MKIKTGARIL ALSALTTMMF SASALAKIEE GKLVIWINGD KGYNGLAEVG KKFEKDTGIK 
61:	VTVEHPDKLE EKFPQVAATG DGPDIIFWAH DRFGGYAQSG LLAEITPDKA FQDKLYPFTW 
121:	DAVRYNGKLI AYPIAVEALS LIYNKDLLPN PPKTWEEIPA LDKELKAKGK SALMFNLQEP 
181:	YFTWPLIAAD GGYAFKYENG KYDIKDVGVD NAGAKAGLTF LVDLIKNKHM NADTDYSIAE 
241:	AAFNKGETAM TINGPWAWSN IDTSKVNYGV TVLPTFKGQP SKPFVGVLSA GINAASPNKE 
301:	LAKEFLENYL LTDEGLEAVN KDKPLGAVAL KSYEEELAKD PRIAATMENA QKGEIMPNIP 
361:	QMSAFWYAVR TAVINAASGR QTVDEALKDA QTRITK