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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:P68187
Protein Name:Maltose/maltodextrin import ATP-binding protein MalK aka B4035
Length:371
Molecular Weight:40990.00
Species:Escherichia coli [83333]
Location1 / Topology2 / Orientation3: Cell inner membrane1 / Peripheral membrane protein2
Substrate Maltooligosaccharides, Maltose

Cross database links:

DIP: DIP-47850N
RefSeq: AP_004536.1    NP_418459.1   
Entrez Gene ID: 948537   
Pfam: PF00005    PF08402    TesT    TesT   
BioCyc: EcoCyc:MALK-MONOMER    ECOL168927:B4035-MONOMER   
KEGG: ecj:JW3995    eco:b4035   

Gene Ontology

GO:0043190 C:ATP-binding cassette (ABC) transporter complex
GO:0005886 C:plasma membrane
GO:0005524 F:ATP binding
GO:0015609 F:maltooligosaccharide-importing ATPase activity
GO:0015423 F:maltose-transporting ATPase activity
GO:0042956 P:maltodextrin transport
GO:0015768 P:maltose transport

References (17)

[1] “Sequence of the malK gene in E.coli K12.”  Gilson E.et.al.   6296778
[2] “Comparison of sequences from the malB regions of Salmonella typhimurium and Enterobacter aerogenes with Escherichia coli K12: a potential new regulatory site in the interoperonic region.”  Dahl M.K.et.al.   2674653
[3] “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
[4] “The complete genome sequence of Escherichia coli K-12.”  Blattner F.R.et.al.   9278503
[5] “Highly accurate genome sequences of Escherichia coli K-12 strains MG1655 and W3110.”  Hayashi K.et.al.   16738553
[6] “A DNA sequence containing the control regions of the malEFG and malK-lamB operons in Escherichia coli K12.”  Bedouelle H.et.al.   6283312
[7] “Overproduction, solubilization, and reconstitution of the maltose transport system from Escherichia coli.”  Davidson A.L.et.al.   2155217
[8] “Regulation of the maltose transport system of Escherichia coli by the glucose-specific enzyme III of the phosphoenolpyruvate-sugar phosphotransferase system. Characterization of inducer exclusion-resistant mutants and reconstitution of inducer exclusion in proteoliposomes.”  Dean D.A.et.al.   2250006
[9] “Purification and characterization of the membrane-associated components of the maltose transport system from Escherichia coli.”  Davidson A.L.et.al.   2026607
[10] “The activities of the Escherichia coli MalK protein in maltose transport, regulation, and inducer exclusion can be separated by mutations.”  Kuehnau S.et.al.   2007546
[11] “The ATP-binding cassette subunit of the maltose transporter MalK antagonizes MalT, the activator of the Escherichia coli mal regulon.”  Panagiotidis C.H.et.al.   9822819
[12] “Subunit interactions in ABC transporters: a conserved sequence in hydrophobic membrane proteins of periplasmic permeases defines an important site of interaction with the ATPase subunits.”  Mourez M.et.al.   9214624
[13] “ATP modulates subunit-subunit interactions in an ATP-binding cassette transporter (MalFGK2) determined by site-directed chemical cross-linking.”  Hunke S.et.al.   10809785
[14] “Structural model of MalK, the ABC subunit of the maltose transporter of Escherichia coli: implications for mal gene regulation, inducer exclusion, and subunit assembly.”  Boehm A.et.al.   11709552
[15] “Protein complexes of the Escherichia coli cell envelope.”  Stenberg F.et.al.   16079137
[16] “Maltose/maltodextrin system of Escherichia coli: transport, metabolism, and regulation.”  Boos W.et.al.   9529892
[17] “A tweezers-like motion of the ATP-binding cassette dimer in an ABC transport cycle.”  Chen J.et.al.   14527411
Structure:
1Q12   1Q1B   1Q1E   2AWN   2AWO   2R6G   3FH6   3GD7   3PUV   3PUW   [...more]

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FASTA formatted sequence
1:	MASVQLQNVT KAWGEVVVSK DINLDIHEGE FVVFVGPSGC GKSTLLRMIA GLETITSGDL 
61:	FIGEKRMNDT PPAERGVGMV FQSYALYPHL SVAENMSFGL KLAGAKKEVI NQRVNQVAEV 
121:	LQLAHLLDRK PKALSGGQRQ RVAIGRTLVA EPSVFLLDEP LSNLDAALRV QMRIEISRLH 
181:	KRLGRTMIYV THDQVEAMTL ADKIVVLDAG RVAQVGKPLE LYHYPADRFV AGFIGSPKMN 
241:	FLPVKVTATA IDQVQVELPM PNRQQVWLPV ESRDVQVGAN MSLGIRPEHL LPSDIADVIL 
301:	EGEVQVVEQL GNETQIHIQI PSIRQNLVYR QNDVVLVEEG ATFAIGLPPE RCHLFREDGT 
361:	ACRRLHKEPG V