PDBsum entry 1q1e

Transport protein

PDB id: 1q1e

Contents

Protein chains

367 a.a. *

* Residue conservation analysis

PDB id:

1q1e

Name:

Transport protein

Title:

The atpase component of e. Coli maltose transporter (malk) in the nucleotide-free form

Structure:

Maltose/maltodextrin transport atp-binding protein malk. Chain: a, b. Engineered: yes

Source:

Escherichia coli. Organism_taxid: 83333. Strain: k12. Gene: malk or b4035 or z5633 or ecs5018. Expressed in: escherichia coli. Expression_system_taxid: 562.

Resolution:

2.90Å R-factor: 0.244 R-free: 0.276

Authors:

J.Chen,G.Lu,J.Lin,A.L.Davidson,F.A.Quiocho

Key ref:

J.Chen et al. (2003). A tweezers-like motion of the ATP-binding cassette dimer in an ABC transport cycle. Mol Cell, 12, 651-661. PubMed id: 14527411 DOI: 10.1016/j.molcel.2003.08.004

Date:

19-Jul-03 Release date: 30-Sep-03

Protein chains

P68187  (MALK_ECOLI) -  Maltose/maltodextrin import ATP-binding protein MalK from Escherichia coli (strain K12)

Seq: 371 a.a.

Struc: 367 a.a.

Enzyme reactions

• Enzyme class: E.C.7.5.2.1 - ABC-type maltose transporter.
• Reaction: D-maltose(out) + ATP + H2O = D-maltose(in) + ADP + phosphate + H⁺

Molecule diagrams generated from .mol files obtained from the KEGG ftp site

reference

DOI no: 10.1016/j.molcel.2003.08.004

Mol Cell 12:651-661 (2003)

PubMed id: 14527411

A tweezers-like motion of the ATP-binding cassette dimer in an ABC transport cycle.

J.Chen, G.Lu, J.Lin, A.L.Davidson, F.A.Quiocho.

ABSTRACT

The ATPase components of ATP binding cassette (ABC) transporters power the transporters by binding and hydrolyzing ATP. Major conformational changes of an ATPase are revealed by crystal structures of MalK, the ATPase subunit of the maltose transporter from Escherichia coli, in three different dimeric configurations. While other nucleotide binding domains or subunits display low affinity for each other in the absence of the transmembrane segments, the MalK dimer is stabilized through interactions of the additional C-terminal domains. In the two nucleotide-free structures, the N-terminal nucleotide binding domains are separated to differing degrees, and the dimer is maintained through contacts of the C-terminal regulatory domains. In the ATP-bound form, the nucleotide binding domains make contact and two ATPs lie buried along the dimer interface. The two nucleotide binding domains of the dimer open and close like a pair of tweezers, suggesting a regulatory mechanism for ATPase activity that may be tightly coupled to translocation.

Selected figure(s)

Figure 4.
Figure 4. Closed, Semi-Open, and Open Structures of MalK Homodimer with Superimposed RDsThe distances between two H89 residues in a homodimer are indicated.(A) Superimposed closed form with bound ATP (yellow) and semi-open form without bound ATP (blue). The excellent overlap of the RDs is evident by the green color resulting from the combination of yellow and blue colors.(B) Overlay of the semi-open (blue) and the open (red) nucleotide-free structures.

Figure 5.
Figure 5. A Model of the Interaction between the EAA Loops of MalF and MalG Transmembrane Proteins and the Q Loop of MalK(A) Model of the docking of the L loop of BtuC to the Q loop of MalK. To obtain this model, the NBD of MalK from the ATP-bound structure was aligned with the NBD of BtuCD. Color codes: cyan, the BtuC L loop; blue, the Q loop of MalK; red and purple, the Walker A motif of one subunit and the LSGGQ motif of the other subunit, respectively. ATP is shown in ball-and-stick.(B) Predicted helix-loop-helix motif of the EAA loops of MalF and MalG. The L loop in the crystal structure of BtuCD, which displays a helix-loop-helix configuration (Locher et al., 2002), is the equivalent of the EAA loops.

The above figures are reprinted by permission from Cell Press: Mol Cell (2003, 12, 651-661) copyright 2003.

Figures were selected by an automated process.