 |
PDBsum entry 2z8v
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
 |
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
Immune system
|
PDB id
|
|
|
|
2z8v
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
References listed in PDB file
|
|
|
Key reference
|
|
|
Title
|
|
Structure of an ignar-Ama1 complex: targeting a conserved hydrophobic cleft broadens malarial strain recognition.
|
|
|
Authors
|
|
K.A.Henderson,
V.A.Streltsov,
A.M.Coley,
O.Dolezal,
P.J.Hudson,
A.H.Batchelor,
A.Gupta,
T.Bai,
V.J.Murphy,
R.F.Anders,
M.Foley,
S.D.Nuttall.
|
|
|
Ref.
|
|
Structure, 2007,
15,
1452-1466.
[DOI no: ]
|
|
|
PubMed id
|
|
|
|
|
|
Abstract
|
|
|
Apical membrane antigen 1 (AMA1) is essential for invasion of erythrocytes and
hepatocytes by Plasmodium parasites and is a leading malarial vaccine candidate.
Although conventional antibodies to AMA1 can prevent such invasion, extensive
polymorphisms within surface-exposed loops may limit the ability of these
AMA1-induced antibodies to protect against all parasite genotypes. Using an
AMA1-specific IgNAR single-variable-domain antibody, we performed targeted
mutagenesis and selection against AMA1 from three P. falciparum strains. We
present cocrystal structures of two antibody-AMA1 complexes which reveal
extended IgNAR CDR3 loops penetrating deep into a hydrophobic cleft on the
antigen surface and contacting residues conserved across parasite species.
Comparison of a series of affinity-enhancing mutations allowed dissection of
their relative contributions to binding kinetics and correlation with inhibition
of erythrocyte invasion. These findings provide insights into mechanisms of
single-domain antibody binding, and may enable design of reagents targeting
otherwise cryptic epitopes in pathogen antigens.
|
|
|
|
|
|
|
|
Figure 5.
Figure 5. V[NAR]-AMA1 Contacts
(A) Alignment of AMA1s
from P. falciparum strains 3D7, W2mef, and HB3 (residues
N104–E438). Residues polymorphic between strains are boxed.
Conserved hydrophobic cleft residues are underlined and
asterisked. Residues in contact with V[NAR]s 14I-1 and 14I1-M15
(magenta), 14I-1 only (red), or 14I1-M15 only (blue) are
indicated.
(B) Stereo images of the 14I-1 backbone (red)
penetrating the AMA1 hydrophobic cleft (gray). Side chains of
AMA1 residues within 4 Å of the V[NAR] backbone are shown,
including hydrophobic residues forming the base of the
hydrophobic cleft (orange) and residues polymorphic between P.
falciparum strains 3D7, W2mef, and HB3 (cyan).
(C) As for
(B) except for 14I1-M15 backbone (blue).
|
|
Figure 6.
Figure 6. Mechanism of V[NAR] Binding
(A) V[NAR] residue
Arg92 contacts AMA1 residues Asn173, Glu174, Pro185, Thr186, and
Glu187 (<4 Å) in a series of hydrogen bond and salt bridge
interactions in the 14I-1 crystallographic structure. Residue
coloring is as for Figure 5.
(B) As for (A) except for the
V[NAR] 14I1-M15 structure.
(C) V[NAR] residues Tyr94,
Tyr96, and Leu98 in the 14I-1 structure contact hydrophobic
cleft residues Phe183 and Tyr251, and associated residue Asn371,
through a network of water-mediated hydrogen bonds and potential
aromatic interactions.
(D) V[NAR] residues Leu89 and Phe100
in the 14I-1 structure are closely associated with AMA1 residues
within the hydropobic cleft (Met190, Tyr202, Met224) and
residues polymorphic between P. falciparum strains (Met190,
Phe201).
|
|
|
|
|
|
The above figures are
reprinted
by permission from Cell Press:
Structure
(2007,
15,
1452-1466)
copyright 2007.
|
|
|
|
|
|
|
