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

OverviewOverview

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.

About this StructureAbout this Structure

2AWN is a Single protein structure of sequence from Escherichia coli with and as ligands. Active as Maltose-transporting ATPase, with EC number 3.6.3.19 Full crystallographic information is available from OCA.

ReferenceReference

ATP hydrolysis is required to reset the ATP-binding cassette dimer into the resting-state conformation., Lu G, Westbrooks JM, Davidson AL, Chen J, Proc Natl Acad Sci U S A. 2005 Dec 13;102(50):17969-74. Epub 2005 Dec 2. PMID:16326809

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 caption="2awn, resolution 2.30&Aring;" />
 '''Crystal structure of the ADP-Mg-bound E. Coli MALK (Crystallized with ATP-Mg)'''<br />
 ==Overview==
-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.
+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.
 ==About this Structure==
-AWN is a [http://en.wikipedia.org/wiki/Single_protein Single protein] structure of sequence from [http://en.wikipedia.org/wiki/Escherichia_coli Escherichia coli] with MG and ADP as [http://en.wikipedia.org/wiki/ligands ligands]. Active as [http://en.wikipedia.org/wiki/Maltose-transporting_ATPase Maltose-transporting ATPase], with EC number [http://www.brenda-enzymes.info/php/result_flat.php4?ecno=3.6.3.19 3.6.3.19] Full crystallographic information is available from [http://ispc.weizmann.ac.il/oca-bin/ocashort?id=2AWN OCA].
+AWN is a [http://en.wikipedia.org/wiki/Single_protein Single protein] structure of sequence from [http://en.wikipedia.org/wiki/Escherichia_coli Escherichia coli] with <scene name='pdbligand=MG:'>MG</scene> and <scene name='pdbligand=ADP:'>ADP</scene> as [http://en.wikipedia.org/wiki/ligands ligands]. Active as [http://en.wikipedia.org/wiki/Maltose-transporting_ATPase Maltose-transporting ATPase], with EC number [http://www.brenda-enzymes.info/php/result_flat.php4?ecno=3.6.3.19 3.6.3.19] Full crystallographic information is available from [http://oca.weizmann.ac.il/oca-bin/ocashort?id=2AWN OCA].
 ==Reference==
@@ Line 15: / Line 15: @@
 [[Category: Single protein]]
 [[Category: Chen, J.]]
-[[Category: Davidson, A.L.]]
+[[Category: Davidson, A L.]]
 [[Category: Lu, G.]]
-[[Category: Westbrooks, J.M.]]
+[[Category: Westbrooks, J M.]]
 [[Category: ADP]]
 [[Category: MG]]
 [[Category: atp-binding cassette]]
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