1.
Matthew
KimA,
Kristen
Procko*
and
Stephen
F.
Martin‡
A
=
Synthesis
and
Biological
Recognition,
*
=
Research
Educator,
‡
=
Principal
Investigator
The
main
goal
of
this
study
is
to
determine
the
thermodynamics
of
protein-­‐
ligand
interactions
to
the
stream’s
target
protein,
the
mouse
major
urinary
protein-­‐I
(MUP-­‐I),
which
functions
in
the
protection,
transport,
and
slow
release
of
pheromones.
Studying
MUP-­‐I
can
introduce
a
more
clear
understanding
of
the
unorthodox
non-­‐classical
hydrophobic
effect,
in
which
the
protein-­‐ligand
interaction
is
driven
enthalpically
as
opposed
to
entropically.
This
sparked
interest
in
structurally
changing
various
ligands
in
order
to
study
the
thermodynamic
behavior
arising
from
their
interactions
to
MUP-­‐I.
An
analogue
of
a
high-­‐binding
ligand,
2-­‐sec-­‐butyldihydrothiazole
(SBT),
was
synthesized.
It
was
predicted
that
because
of
the
analog’s
unique
structure,
an
increase
in
the
enthalpic
stabilization
could
occur,
leading
to
a
higher
binding
afRinity
than
that
of
SBT.
General
characteristics:
§ Functions
in
the
protection,
transport,
and
slow
release
of
pheromones
§ Single
α-­‐helix
and
eight
β-­‐sheets
§ Forms
hydrophobic
barrel
§ Active
sites
hydrated
with
two
water
molecules
§ Exhibits
hydrophobic
effect
Important
active
site
characteristics:
§ Hydrogen
bond
network
consists
of
Phe56,
Leu58,
and
Tyr138
§ Van
der
Waals
interactions
with
multiple
residues
in
the
active
site:
§ Leu72,
Val100,
Phe108,
Leu121,
leu123,
and
Leu134
• Ligand
is
normally
introduced
incrementally
into
a
solution
of
MUP-­‐I;
the
heat
released
upon
binding
is
recorded.
• Free
energy
is
determined
through
values
derived
from
the
Gibbs
free
energy
equation,
ΔG
=
ΔH
–
TΔS
=
-­‐RT(lnKa).
• Change
in
free
energy
(ΔG),
which
is
inRluenced
by
the
change
in
enthalpy
(ΔH)
and
change
in
entropy
(ΔS),
reveals
the
driving
forces
for
a
particular
ligand’s
binding
to
the
active
site
of
MUP-­‐I.
S
N
Leu72
Leu134
Phe108
Val100
Ala121
H
O
H
O
H O
H
O
H O
Leu58
Tyr138
Leu123
NH
NH
Phe56
Abstract1
Mouse
Major
Urinary
Protein
–
I1,3,4
Observed
Trends4
Isothermal
Titration
Calorimetry
(ITC)2,3
ITC
Data
Acknowledgements
References:
1Timm,
D.E.;
Baker,
L.J.;
Mueller,
H.;
Zidek,
L.;
Novotny,
M.V.
Structural
basis
of
pheromone
binding
to
mouse
major
urinary
protein
(MUP-­‐I).
Protein
Sci.
2001,
10,
997-­‐1004.
2Pierce,
M.M.;
Raman,
C.S.;
Nall,
B.T.
Isothermal
Titration
Calorimetry
of
Protein-­‐Protein
Interactions.
Methods
1999,
19,
213-­‐221.
3Homans,
W.S.
Water,
water
everywhere
–
except
where
it
matters?
Drug
discovery
today
2007,
12,
13-­‐14.
4Sharrow,
S.D.;
Novotny,
M.V.;
Stone,
M.
J.
Thermodynamic
analysis
of
binding
between
mouse
major
urinary
protein-­‐I
and
the
pheromone
2-­‐sec-­‐
butyl-­‐4,5-­‐dihydrothiazole.
Biochemistry
2003,
42,
6302-­‐6309.
5Jin,
Sarah.
The
University
of
Texas,
Austin,
TX.
4,5-­‐Dihydro-­‐2-­‐phenylthiazole,
2010.
6Azarm,
Kristopher.
The
University
of
Texas,
Austin,
TX.
Elucidating
the
Thermodynamics
of
Binding
of
2-­‐(Pyridin-­‐3-­‐yl)-­‐4,5-­‐dihydrothiazole,
2011.
N
S HS
H2N
DBH
Reflux, 7 min. 100 oC
N
S
N
4 5 6
Synthetic
Route
S
N
S
N
1 2
S
N N
3
Past
Studies5,6