| dc.description.abstract | Matrix metalloproteinases (MMPs) are a family of Zn2
+ -dependent, Ca2
+ -containing
endoproteinases involved in tissue remodeling and degradation of the extracellular matrix
(ECM). Human MMP isozymes are known to be involved in the progression and metastasis
of many diseases like cancer, Alzheimer's, and etc. The different nanoparticles (e.g. gold
nanoparticles, liposomes, and charged quantum dots) used in this study provides insights
into nanoparticle-induced differential modulation in the structural-functional characteristics
of MMP 7, 9 and 10 for better therapeutic intervention.
To demonstrate the relationship between the rigid and flexible surfaces on the
differential modulation of functional and structural characteristics of MMP-7, polylysine
(PLL) and cationic gold nanoparticles (Au-CNP) were selected as representative examples.
These cationic nano-structures were expected to serve as "soft" (flexible) and ''rigid" (hard)
ligands, respectively. Steady-state kinetic analysis demonstrated that PLL induces
activation and inhibition of MMP-7 at stoichiometric and super-stoichiometric
concentrations respectively. Circular Dichroism spectroscopy was used to confirm that
binding of Au-CNP to MMP-7 induces denaturation of the protein.
In pursuit of understanding the molecular origin of the intrinsic selectivity in
binding of human MMP isozymes to differently charged lipid membranes, steady-state
kinetic studies and intrinsic tryptophan quenching studies were carried out. Results
demonstrated that differently charged lipid membranes bind to all three MMPs; phosphotidylserine (POPS) liposomes are selective for MMP-7. The bipolar distribution of
negative and positive charges on the surface of this enzyme dictates the binding of
liposomes and perturbation of catalytic activity.
An attempt to explain the molecular rationale for alternative binding modes of
differently charged quantum dots (QDs) to the three MMPs, steady-state tryptophan
quenching, steady-state kinetics, and time-resolved fluorescence measurements were
carried out. Differently charged QDs bind to all the three MMP isozymes. Enzyme activity
of these MMPs was perturbed upon binding to cationic and anionic QDs. Binding of
MMPs to the differently charged QDs is reversible and is mediated via electrostatic
interactions. Analysis of time-resolved fluorescence data indicates that the protein
expenences different micro-environments, due to different distribution of intrinsic
tryptophan residues (buried and exposed) on MMP isozymes or the existence of two
distinct conformations of the protein. Binding to charged QDs perturbs enzyme activity of
MMPs either by restricting the access of the substrate to the active-site or through allosteric
modulation. In order to develop new isozyme-selective inhibitors, small molecule
inhibitors (SMis) were designed, synthesized and screened for MMP-7, 9 and 10. Results
indicate that hydroxamates and carboxylates are preferred SMis. Binding preference is
based on either the micro-environments of the active-site pockets. | en_US |
