 |
PDBsum entry 2wmh
|
|
|
|
References listed in PDB file
|
 |
|
Key reference
|
|
|
Title
|
|
Differential recognition and hydrolysis of host carbohydrate antigens by streptococcus pneumoniae family 98 glycoside hydrolases.
|
|
|
Authors
|
|
M.A.Higgins,
G.E.Whitworth,
N.El warry,
M.Randriantsoa,
E.Samain,
R.D.Burke,
D.J.Vocadlo,
A.B.Boraston.
|
|
|
Ref.
|
|
J Biol Chem, 2009,
284,
26161-26173.
[DOI no: ]
|
|
|
PubMed id
|
|
|
|
|
|
|
|
|
Abstract
|
|
|
The presence of a fucose utilization operon in the Streptococcus pneumoniae
genome and its established importance in virulence indicates a reliance of this
bacterium on the harvesting of host fucose-containing glycans. The identities of
these glycans, however, and how they are harvested is presently unknown. The
biochemical and high resolution x-ray crystallographic analysis of two family 98
glycoside hydrolases (GH98s) from distinctive forms of the fucose utilization
operon that originate from different S. pneumoniae strains reveal that one
enzyme, the predominant type among pneumococcal isolates, has a unique
endo-beta-galactosidase activity on the LewisY antigen. Altered active site
topography in the other species of GH98 enzyme tune its endo-beta-galactosidase
activity to the blood group A and B antigens. Despite their different
specificities, these enzymes, and by extension all family 98 glycoside
hydrolases, use an inverting catalytic mechanism. Many bacterial and viral
pathogens exploit host carbohydrate antigens for adherence as a precursor to
colonization or infection. However, this is the first evidence of bacterial
endoglycosidase enzymes that are known to play a role in virulence and are
specific for distinct host carbohydrate antigens. The strain-specific
distribution of two distinct types of GH98 enzymes further suggests that S.
pneumoniae strains may specialize to exploit host-specific antigens that vary
from host to host, a factor that may feature in whether a strain is capable of
colonizing a host or establishing an invasive infection.
|
|
|
|
|
|
|
|
Figure 3.
The structural features of S. pneumoniae family 98 enzymes.A,
divergent stereo schematic representation of the structure of
Sp4GH98. The N-terminal (α/β)[8] barrel housing the catalytic
residues in shown in green, the C-terminal β-sandwich domain in
purple, and the smaller intervening domain in yellow. Shown are
solvent-accessible surface representations (gray) of the active
site of Sp4GH98 containing the H disaccharide (shown in a stick
representation) (B) and Sp3GH98 containing the A trisaccharide
(shown in a stick representation) (C). Green, galactose; blue,
fucose; magenta, N-acetylgalactosamine. The yellow mesh shows
the maximum likelihood (27)/σ[a]-weighted (29) F[o] − F[c]
maps for the carbohydrates (contoured at 3σ; 0.24
electrons/Å^3 for Sp4GH98 and 0.20 electrons/Å^3 for
Sp3GH98). Subsites of the active site are labeled in white. D,
schematic of the interactions in the −1 and −2 subsites of
Sp4GH98 and Sp3GH98. Residues in black are conserved in both
enzymes and labeled in black (Sp4GH98) or gray (Sp3GH98). Red
residues are present only in Sp4GH98. E, schematic of the
−2′ subsite of Sp3GH98. Black residues are shown for
interactions that are conserved for the galactose of the
B-antigen and the N-acetylgalactosamine of the A antigen. The
red residue represents an interaction that is unique to the A
antigen. F, divergent stereo representation of a structural
overlay of the active sites of Sp4GH98 (blue) and Sp3GH98
(orange). The A trisaccharide product in the Sp3GH98 active site
is shown in sticks and colored as in C. The loop protruding from
the β-sandwich domain is shown in a schematic diagram
representation. Trp^512 of Sp4GH98 that blocks the −2′
subsite in this protein is shown in a stick representation.
|
|
Figure 4.
Aglycon recognition in GH98 enzymes. Solvent-accessible
surface representation (gray) of the active site of Sp4GH98E158A
containing the Lewis^Y tetrasaccharide substrate (shown in a
stick representation) (A) and Sp3GH98E558A containing the
A-Lewis^Y pentasaccharide (shown in a stick representation) (B).
Green, galactose; blue, fucose; cyan, N-acetylglucosamine;
magenta, N-acetylgalactosamine. The yellow mesh shows the
maximum likelihood/σ[a]-weighted F[o] − F[c] maps for the
carbohydrates contoured at 2.5σ (0.16 electrons/Å^3) for
Sp4GH98E158A and 3σ (0.22 electrons/Å^3) for
Sp3GH98E558A. Subsites of the active site are labeled in white.
C, representative overlay of the GH98 active site. All GH98
structures were overlaid. Because of the virtually identical
positioning of the active site structures, the Sp3GH98 A
trisaccharide complex was chosen as a reference point to display
key features. The backbone of the Sp3GH98 A trisaccharide
product complex is shown in a schematic diagram with relevant
active site residues shown in a stick representation. The A
trisaccharide sugar is shown as yellow sticks. The A-Lewis^Y
pentasaccharide from the Sp3GH98E558A substrate complex is shown
as green sticks. Residues in Sp3GH98 are labeled in gray, and
analogous residues in Sp4GH98, which were identically
positioned, are labeled in black. Sugar residues in the +1 and
−1 subsites of Sp4GH98 were also positioned virtually
identically to those of the Sp3GH98 complexes. Relevant
interresidue hydrogen bonds and protein-substrate distances are
shown. The putative catalytic acid is colored pink and putative
catalytic bases are colored blue. D, schematic of the
interactions in the +1 and +1′ subsites. Interactions
conserved between Sp4GH98 and Sp3GH98 are shown with green amino
acids. Black amino acids are those only in Sp4GH98, and red
amino acids are those only in Sp3GH98.
|
|
|
|
|
|
The above figures are
reprinted
by permission from the ASBMB:
J Biol Chem
(2009,
284,
26161-26173)
copyright 2009.
|
|
|
|
|
|
|
