THESIS
2013
iv leaves, v-viii, 43 pages : illustrations (some color) ; 30 cm
Abstract
Myo1c is the first mammalian single-headed myosin identified. Although the
cellular function of myosin 1c is not clearly understood, there is evidence showing that
myosin 1c is involved in insulin-mediated GLUT4 exocytosis. The N-terminal of
myo1c is the motor domain responsible for actin-binding and ATP hydrolysis. The
adjacent neck domain contains IQ motifs which bind to CaM. The C-terminal end
contains a PH domain which can bind to plasma membranes.
A suit of biochemistry experiments demonstrate that myo1c can bind 3 copies of
calmodulin (CaM) in the absence of Ca
2+. Our unpublished the X-ray crystal structure
of the myo1c tail shows that the bindings between the first two IQ motifs and CaM
follows the canonical CaM/IQ-motif binding mode, in which the N-lobe of CaM binds...[
Read more ]
Myo1c is the first mammalian single-headed myosin identified. Although the
cellular function of myosin 1c is not clearly understood, there is evidence showing that
myosin 1c is involved in insulin-mediated GLUT4 exocytosis. The N-terminal of
myo1c is the motor domain responsible for actin-binding and ATP hydrolysis. The
adjacent neck domain contains IQ motifs which bind to CaM. The C-terminal end
contains a PH domain which can bind to plasma membranes.
A suit of biochemistry experiments demonstrate that myo1c can bind 3 copies of
calmodulin (CaM) in the absence of Ca
2+. Our unpublished the X-ray crystal structure
of the myo1c tail shows that the bindings between the first two IQ motifs and CaM
follows the canonical CaM/IQ-motif binding mode, in which the N-lobe of CaM binds
to C-terminus and the C-lobe of CaM binds to N-terminus of IQ-motif, respectively.
Unexpectedly, the third IQ-motif of myo1c binds to CaM in a novel binding mode.
Instead of binding to the C-terminal half of IQ3, the N-lobe of the CaM binds to a
parallel two helix bundle immediately following IQ3.
Static light scattering method and NMR spectroscopy were used to investigate how
myo1c responds to Ca
2+ binding. The data indicate that upon Ca
2+ influx, myo1c bind to
two CaM. Apo-CaM bound to IQ1 and IQ2 will dissociate upon Ca
2+ concentration
rises. The CaM which binds to IQ3 and postIQ will change its conformation upon Ca
2+
concentration increases, and the IQ3 motif can engage both lobes of CaM. More
interestingly, the postIQ motif becomes capable of binding to one molecular of
Ca
2+-CaM with high affinity.
The results presented in this thesis will demonstrate that myo1c can undergo a
significant Ca
2+ mediated conformation changes via its light chain CaM.
Post a Comment