 |
PDBsum entry 3csl
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
 |
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
Membrane protein/heme binding protein
|
PDB id
|
|
|
|
3csl
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
References listed in PDB file
|
|
|
Key reference
|
|
|
Title
|
|
Heme uptake across the outer membrane as revealed by crystal structures of the receptor-Hemophore complex.
|
|
|
Authors
|
|
S.Krieg,
F.Huché,
K.Diederichs,
N.Izadi-Pruneyre,
A.Lecroisey,
C.Wandersman,
P.Delepelaire,
W.Welte.
|
|
|
Ref.
|
|
Proc Natl Acad Sci U S A, 2009,
106,
1045-1050.
[DOI no: ]
|
|
|
PubMed id
|
|
|
|
|
|
Abstract
|
|
|
Gram-negative bacteria use specific heme uptake systems, relying on outer
membrane receptors and excreted heme-binding proteins (hemophores) to scavenge
and actively transport heme. To unravel the unknown molecular details involved,
we present 3 structures of the Serratia marcescens receptor HasR in complex with
its hemophore HasA. The transfer of heme over a distance of 9 A from its
high-affinity site in HasA into a site of lower affinity in HasR is coupled with
the exergonic complex formation of the 2 proteins. Upon docking to the receptor,
1 of the 2 axial heme coordinations of the hemophore is initially broken, but
the position and orientation of the heme is preserved. Subsequently, steric
displacement of heme by a receptor residue ruptures the other axial
coordination, leading to heme transfer into the receptor.
|
|
|
|
|
|
|
|
Figure 1.
Structure of the ternary complex HasA∼HasR∼heme. HasA
(red) and HasR (cork domain beginning with residue Asn-113 in
orange; barrel domain beginning at residue Lys-241 in blue) are
indicated as a ribbon model. The first 5 strands and the loops
L1–L3 of HasR are omitted to allow a view into the barrel
interior. The heme is indicated as a wire frame model (green).
The extracellular loops 6–11 are labeled. Yellow parts of or
near L6, L8, and L9 mark positions of 6 residue deletions that
have been found to abolish HasA binding to the receptor.
|
|
Figure 4.
Detail of the HasA∼HasR∼heme complex showing a putative
heme access channel extending from the external medium between
L3 and the bent loop L4 to the receptor heme-binding site. HasA
and HasR are indicated as a CPK model in red and blue,
respectively, except for the heme-coordinating HasR histidines
that are colored yellow. The heme is indicated as a wire frame
model in green and the Fe^3+ atom as a red sphere.
|
|
|
|
|
|
|
|
|
|
