McKnight Lab Reseach

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I. Actin-Binding by Headpiece Motifs

actin-binding surface of villin headpiece

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 kinases.

II. A Minimalist Folded Protein

NMR structure of 35-residue villin headpiece subdomain, HP36

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

Model of ApoB-17 bound to a lipid emulsion particle

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.

completed projects

Last Revised 04/14/05

2000 Jamie McKnight