 |
PDBsum entry 1vcu
|
|
|
|
References listed in PDB file
|
 |
|
Key reference
|
|
|
Title
|
|
Crystal structure of the human cytosolic sialidase neu2. Evidence for the dynamic nature of substrate recognition.
|
|
|
Authors
|
|
L.M.Chavas,
C.Tringali,
P.Fusi,
B.Venerando,
G.Tettamanti,
R.Kato,
E.Monti,
S.Wakatsuki.
|
|
|
Ref.
|
|
J Biol Chem, 2005,
280,
469-475.
[DOI no: ]
|
|
|
PubMed id
|
|
|
|
|
|
Abstract
|
|
|
Gangliosides play key roles in cell differentiation, cell-cell interactions, and
transmembrane signaling. Sialidases hydrolyze sialic acids to produce asialo
compounds, which is the first step of degradation processes of glycoproteins and
gangliosides. Sialidase involvement has been implicated in some lysosomal
storage disorders such as sialidosis and galactosialidosis. Neu2 is a recently
identified human cytosolic sialidase. Here we report the first high resolution
x-ray structures of mammalian sialidase, human Neu2, in its apo form and in
complex with an inhibitor, 2-deoxy-2,3-dehydro-N-acetylneuraminic acid (DANA).
The structure shows the canonical six-blade beta-propeller observed in viral and
bacterial sialidases with its active site in a shallow crevice. In the complex
structure, the inhibitor lies in the catalytic crevice surrounded by ten amino
acids. In particular, the arginine triad, conserved among sialidases, aids in
the proper positioning of the carboxylate group of DANA within the active site
region. The tyrosine residue, Tyr(334), conserved among mammalian and bacterial
sialidases as well as in viral neuraminidases, facilitates the enzymatic
reaction by stabilizing a putative carbonium ion in the transition state. The
loops containing Glu(111) and the catalytic aspartate Asp(46) are disordered in
the apo form but upon binding of DANA become ordered to adopt two short
alpha-helices to cover the inhibitor, illustrating the dynamic nature of
substrate recognition. The N-acetyl and glycerol moieties of DANA are recognized
by Neu2 residues not shared by bacterial sialidases and viral neuraminidases,
which can be regarded as a key structural difference for potential drug design
against bacteria, influenza, and other viruses.
|
|
|
|
|
|
|
|
Figure 1.
FIG. 1. Sialic acid and inhibitors. Schematic structure of
a sialylgalactose (a), NANA (b), and DANA (c). In the case of
the sialylgalactose, the dotted line indicates the bond
hydrolyzed by the sialidase.
|
|
Figure 4.
FIG. 4. Structural changes of Neu2 upon maltose and DANA
binding. a, ribbon diagram of Neu2 apo form, viewed from the
side. The active site is located on the top part of the protein.
Secondary elements are colored as in Fig. 2. b, Neu2
sugar-induced form in the same orientation as in a. The arrow
indicates the loop containing Glu111 that becomes ordered and
forms helix  2. c, Neu2-DANA complex
in the same orientation as in a. DANA is represented as a
ball-and-stick model. The arrows indicate two helices ( 1 and
2)
that are formed upon inhibitor binding.
|
|
|
|
|
|
The above figures are
reprinted
by permission from the ASBMB:
J Biol Chem
(2005,
280,
469-475)
copyright 2005.
|
|
|
|
|
|
|
