 |
PDBsum entry 1xef
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
 |
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
Transport protein
|
PDB id
|
|
|
|
1xef
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
References listed in PDB file
|
|
|
Key reference
|
|
|
Title
|
|
H662 is the linchpin of ATP hydrolysis in the nucleotide-Binding domain of the abc transporter hlyb.
|
|
|
Authors
|
|
J.Zaitseva,
S.Jenewein,
T.Jumpertz,
I.B.Holland,
L.Schmitt.
|
|
|
Ref.
|
|
EMBO J, 2005,
24,
1901-1910.
[DOI no: ]
|
|
|
PubMed id
|
|
|
|
|
|
Abstract
|
|
|
The ABC transporter HlyB is a central element of the HlyA secretion machinery, a
paradigm of Type I secretion. Here, we describe the crystal structure of the
HlyB-NBD (nucleotide-binding domain) with H662 replaced by Ala in complex with
ATP/Mg2+. The dimer shows a composite architecture, in which two intact ATP
molecules are bound at the interface of the Walker A motif and the C-loop,
provided by the two monomers. ATPase measurements confirm that H662 is essential
for activity. Based on these data, we propose a model in which E631 and H662,
highly conserved among ABC transporters, form a catalytic dyad. Here, H662 acts
as a 'linchpin', holding together all required parts of a complicated network of
interactions between ATP, water molecules, Mg2+, and amino acids both in cis and
trans, necessary for intermonomer communication. Based on biochemical
experiments, we discuss the hypothesis that substrate-assisted catalysis, rather
than general base catalysis might operate in ABC-ATPases.
|
|
|
|
|
|
|
|
Figure 1.
Figure 1 Crystal structure of the HlyB-NBD H662A dimer with
bound ATP/Mg2+. ATP in stick representation and Mg2+ (green
spheres) are sandwiched at the interface of the two HlyB-NBD
monomers (shown in light tan and light yellow). N- and C-termini
of the individual monomers are labeled. Conserved motifs are
colored in red (Walker A motif; Walker et al, 1982), brown
(Q-loop), blue (C-loop or ABC signature motif), magenta (Walker
B), black (D-loop), and green (H-loop) and labeled accordingly.
The figure was prepared using PyMol (www.pymol.org).
|
|
Figure 2.
Figure 2 (A) Stereo view of one of the ATP-binding sites in the
HlyB-NBD H662A dimer. ATP is shown in stick representation, Mg2+
as a green sphere, and water molecules as blue spheres. (B)
Schematic diagram of the interactions between one of the two
ATP/Mg2+ complexes and HlyB-NBD H662A. (C) Schematic diagram of
the interactions across the monomer -monomer interface. Color
coding is identical to Figure 1. Residues involved in monomer
-monomer contact are highlighted by gray boxes, while residues
involved in protein -ATP contacts are colored in boxes according
to Figure 1. Blue numbers indicate water molecules. Hydrogen
bonds and salt bridges are shown as solid lines, while van der
Waals and hydrophobic interactions are shown as dashed lines.
Letters represent the atoms involved in the interaction.
|
|
|
|
|
|
The above figures are
reprinted
from an Open Access publication published by Macmillan Publishers Ltd:
EMBO J
(2005,
24,
1901-1910)
copyright 2005.
|
|
|
|
|
|
|
