 |
PDBsum entry 2bea
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
 |
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
Hydrolase inhibitor
|
PDB id
|
|
|
|
2bea
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
References listed in PDB file
|
|
|
Key reference
|
|
|
Title
|
|
Spacer asn determines the fate of kunitz (sti) inhibitors, As revealed by structural and biochemical studies on wci mutants.
|
|
|
Authors
|
|
J.Dasgupta,
S.Khamrui,
J.K.Dattagupta,
U.Sen.
|
|
|
Ref.
|
|
Biochemistry, 2006,
45,
6783-6792.
[DOI no: ]
|
|
|
PubMed id
|
|
|
|
|
|
Abstract
|
|
|
The scaffold of serine protease inhibitors plays a significant role in the
process of religation which resists proteolysis of the inhibitor in comparison
to a substrate. Although the role of the conserved scaffolding Asn residue was
previously implicated in the maintenance of the binding loop conformation of
Kunitz (STI) inhibitors, its possible involvement in the prevention of
proteolysis is still unexplored. In this paper, we have investigated the
specific role of the spacer Asn in the prevention of proteolysis through
structural and biochemical studies on the mutants where Asn14 of winged bean
chymotrypsin inhibitor (WCI) has been replaced by Gly, Ala, Thr, Leu, and Gln. A
residue having no side chain or beta-branching at the 14th position creates
deformation and insufficient protrusion of the binding loop, and as a result
N14G and N14T lose the ability to recognize proteases. Although the reactive
site loop conformation of N14A and N14Q are almost identical to WCI, biochemical
results present N14A as a substrate indicating that the methyl group of Ala14 is
not suitable to capture the cleaved parts together for religation. The poor
inhibitory power of N14L points toward the chemical incompatibility of Leu at
the 14th position, although its size is the same as Asn; on the other hand,
slight loss of inhibitory potency of N14Q is attributed to the inappropriate
placement of the Gln14 polar head, caused by the strained accommodation of its
bigger side chain. These observations collectively allow us to conclude that the
side chain of spacer Asn fits snugly into the concave space of the reactive site
loop cavity and its ND2 atom forms hydrogen bonds with the P2 and P1' carbonyl O
at either side of the scissile bond holding the cleaved products together for
religation. Through database analysis, we have identified such spacer
asparagines in five other families of serine protease inhibitors with a similar
disposition of their ND2 atoms, which supports our proposition.
|
|
|
Secondary reference #1
|
|
|
Title
|
|
Single mutation at p1 of a chymotrypsin inhibitor changes it to a trypsin inhibitor: X-Ray structural (2.15 a) and biochemical basis.
|
|
|
Authors
|
|
S.Khamrui,
J.Dasgupta,
J.K.Dattagupta,
U.Sen.
|
|
|
Ref.
|
|
Biochim Biophys Acta, 2005,
1752,
65-72.
|
|
|
PubMed id
|
|
|
|
|
|
|
|
|
|
|
|
|
