Actin cytoskeleton plays a central role in fundamental physiological…
Actin cytoskeleton plays a central role in fundamental physiological processes
mostly short lived
Actin binding protein: responsible for the formation of bundles
fimbrins, formins and villin
whether these proteins cooperate to generate bundles or whether they form different types of bundles that act at different locations to perform specific functions is not clear
There is a need to perform rigorous biochemical characterization of the different isovariants as they might have distinct activities and/or forms of regulation
is a class that is multi-functional and widely expressed in most eukaryotic cells
bind actin filaments and sever and cap the barbed ends of actin filaments in the presence of micromolar concentrations of Ca2+
Fusion proteins of green fluorescent protein with fill-length VLN3 and several VHP constructs decorate actin filaments in plant and animal cells, thus demonstrating their ability to bind actin filaments
The ability of different villin isovariants to bundle, sever, or nucleate actin filaments in vivo has not been tested
Recent studies demonstrate VLN1 is a simple bundling protein in
that is also capable of protecting actin filament from ADF1. It also suggested that VLN1 does not have capping or severing activities and is not regulated by Ca2+
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Biochemical analyses demonstrated that VLN3 bundles actin filaments independently of Ca2+ and that it severs filaments in the presence of micromolar Ca2+
Villins have a C-Terminal headpiece domain that contributes an additional actin binding site and facilitates the formation of higher-order structures by cross-linking actin filaments into bundles
maintenance of cellular architecture and polarity
longer lived, prominent higher-order structures made of actin filaments packed closely together
Bundles are important for various cell processes including:
tracks for organelle movement
positioning of organelles and
Hypothesis: "we hypothesize that these isovariants perform the same function in cells viz bundling actin filaments.
at micromolar Ca2+ levels, however, we predict that VLN3 will sever filaments even in the presence of VLN1"