I. Actin-Binding by Headpiece Motifs
One focus in the lab centers on the intriguing, modular F-actin binding
“headpiece” motif. The headpiece motif is a compact (~70 amino acid) domain
localized at the extreme C-terminus of much larger “core” domains from
several functionally diverse classes of actin-binding proteins. These
headpiece-containing proteins include villin, supervillin, dematin, limatin and
TalB, and their functions range from maintenance of the cytoskeleton and
cell-cell adherens junctions, to potential roles in development. We are
interested in determining the three dimensional structures of headpiece motifs
and detailing their interaction with actin, their core domains, and regulatory
II. A Minimalist Folded Protein
Another area of interest is the development of minimal length folded proteins to
bridge the gap between experimental and computational approaches to protein
folding. We have shown that headpiece domain of villin contains a "subdomain"
of only 35 residues that folds to form a novel three helix structure. The villin
subdomain is one of the shortest amino acid sequences to fold to a monomeric
native state in the absence of disulfide bonds or bound metals/ligands. We are
using a mutational approach to address the question of how this short sequence
encodes the information for a fully folded protein.
III. Modeling Low Density Lipoprotein (LDL) Assembly & Secretion
LDL is the major cholesterol transporting lipoprotein, and high LDL levels are correleated
with Arthelroscrosis. We are investigating the early events in the formation of LDL and VLDL
particles within the cell. We have modelled the first 17% of ApoB (ApoB-17) onto the
crystal structure lipovitellin, whose sequence is homologous the N-terminal region of ApoB.
We then used our ApoB-17 model to dock to a model lipid emulsion particle. This is one possible
model for nascent LDL particle formation. We have tested the lipovitellin-based model by limited proteolysis and have created
a bank of constructs corresponding to the individual domains for further structural and biophysical study.
Last Revised 04/14/05
©2000 Jamie McKnight