2AWN

Crystal structure of the ADP-Mg-bound E. Coli MALK (Crystallized with ATP-Mg)

Summary for 2AWN

• Entry DOI: 10.2210/pdb2awn/pdb
• Related: 1Q12 1Q1B 1Q1E
• Descriptor: Maltose/maltodextrin import ATP-binding protein malK, MAGNESIUM ION, ADENOSINE-5'-DIPHOSPHATE, ... (4 entities in total)
• Functional Keywords: atp-binding cassette, transport protein
• Biological source: Escherichia coli
• Cellular location: Cell inner membrane; Peripheral membrane protein: P68187
• Total number of polymer chains: 4
• Total formula weight: 170544.16

Authors

Lu, G.,Westbrooks, J.M.,Davidson, A.L.,Chen, J. (deposition date: 2005-09-01, release date: 2005-12-13, Last modification date: 2023-08-23)

Primary citation

Lu, G.,Westbrooks, J.M.,Davidson, A.L.,Chen, J.
ATP hydrolysis is required to reset the ATP-binding cassette dimer into the resting-state conformation.
Proc.Natl.Acad.Sci.Usa, 102:17969-17974, 2005

PubMed Abstract: ATP-binding cassette (ABC) transporters couple ATP binding and hydrolysis to the movement of substances across the membrane; conformational changes clearly play an important role in the transporter mechanism. Previously, we have shown that a dimer of MalK, the ATPase subunit of the maltose transporter from Escherichia coli, undergoes a tweezers-like motion in a transport cycle. The MalK monomer consists of an N-terminal nucleotide binding domain and a C-terminal regulatory domain. The two nucleotide-binding domains in a dimer are either open or closed, depending on whether ATP is present, while the regulatory domains maintain contacts to hold the dimer together. In this work, the structure of MalK in a posthydrolysis state is presented, obtained by cocrystallizing MalK with ATP-Mg(2+). ATP was hydrolyzed in the crystallization drop, and ADP-Mg(2+) was found in the resulting crystal structure. In contrast to the ATP-bound form where two ATP molecules are buried in a closed interface between the nucleotide-binding domains, the two nucleotide-binding domains of the ADP-bound form are open, indicating that ADP, unlike ATP, cannot stabilize the closed form. This conclusion is further supported by oligomerization studies of MalK in solution. At low protein concentrations, ATP promotes dimerization of MalK, whereas ADP does not. The structures of dimeric MalK in the nucleotide-free, ATP-bound, and ADP-bound forms provide a framework for understanding the nature of the conformational changes that occur in an ATP-binding cassette transporter hydrolysis cycle, as well as how conformational changes in MalK are coupled to solute transport.

PubMed: 16326809
DOI: 10.1073/pnas.0506039102

Experimental method

X-RAY DIFFRACTION (2.3 Å)