 |
PDBsum entry 2nq2
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
 |
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
Metal transport
|
PDB id
|
|
|
|
2nq2
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
References listed in PDB file
|
|
|
Key reference
|
|
|
Title
|
|
An inward-Facing conformation of a putative metal-Chelate-Type abc transporter.
|
|
|
Authors
|
|
H.W.Pinkett,
A.T.Lee,
P.Lum,
K.P.Locher,
D.C.Rees.
|
|
|
Ref.
|
|
Science, 2007,
315,
373-377.
[DOI no: ]
|
|
|
PubMed id
|
|
|
|
|
|
Abstract
|
|
|
The crystal structure of a putative metal-chelate-type adenosine triphosphate
(ATP)-binding cassette (ABC) transporter encoded by genes HI1470 and HI1471 of
Haemophilus influenzae has been solved at 2.4 angstrom resolution. The
permeation pathway exhibits an inward-facing conformation, in contrast to the
outward-facing state previously observed for the homologous vitamin B12 importer
BtuCD. Although the structures of both HI1470/1 and BtuCD have been solved in
nucleotide-free states, the pairs of ABC subunits in these two structures differ
by a translational shift in the plane of the membrane that coincides with a
repositioning of the membrane-spanning subunits. The differences observed
between these ABC transporters involve relatively modest rearrangements and may
serve as structural models for inward- and outward-facing conformations relevant
to the alternating access mechanism of substrate translocation.
|
|
|
|
|
|
|
|
Figure 2.
Fig. 2. Visualization of the permeation pathways of HI1470/1
and BtuCD with the program HOLE (12). (A) The permeation pathway
generated by the two HI1471 subunits is narrow at the
periplasmic surface and open to the cytoplasm, which are located
toward the top and bottom of the figure, respectively. (B) In
contrast, the pathway for BtuC is closed at the cytoplasm and
open to the periplasm. The HOLE representation of the pore
surface is shown in a multicolored form that was displayed and
rendered with the program VMD (33). Red, green, and blue
surfaces designate regions of the permeation pathway with
effective radii <0.6, 0.6 to 1.15, and >1.15 Å,
respectively. The calculated diameters at the widest part of the
pathways illustrated for HI1470/1 and BtuCD are  11
and 9 Å, respectively. The permeation pathway in BtuCD is
of sufficient size to accommodate a corrin ring but not the
entire B[12] molecule (9); the ligand for HI1470/1 has not been
identified.
|
|
Figure 3.
Fig. 3. (A) Comparison of the homologous membrane-spanning
subunits HI1471 and BtuC, after superposition of TM2 in subunit
A (to the left) of each structure, as viewed down the molecular
two-fold axis from the periplasm. With the exceptions of TM3 to
TM5, the helices in the A subunits of HI1471 (cyan) and BtuC
(purple) superimpose closely. In contrast, interconversion of
the B subunits (to the right) between these two structures (blue
and red, respectively) requires an 9° twist
(indicated by the curved arrow) about an axis oriented in the
direction shown to the right, which passes through the helical
domain of the ABC subunit. (B) Stereoview of a superposition of
helices TM3, TM4, TM5, TM8, TM10, and 5a in subunit A of HI1471
(cyan) and BtuC (purple), as viewed from within the permeation
pathway with the molecular two-fold axis vertical. The internal
symmetry–relating helices TM3 and TM8 and TM5 and TM10, as
well as the irregular structures of TM3 and TM8, may be
observed. The extramembrane helix 5a helps restrict the
permeation pathway on the periplasmic side of HI1470/1.
|
|
|
|
|
|
The above figures are
reprinted
by permission from the AAAs:
Science
(2007,
315,
373-377)
copyright 2007.
|
|
|
|
|
|
|
