Joanna K. Krueger - Biophysical Chemistry

Actin

A major goal of my lab is to understand the regulatory mechanisms that govern the actin cytoskeleton. Filamentous actin (F-actin) structures within non-muscle cells possess unique biophysical and biochemical properties required for cell locomotion, cell division, compartmentalization, and morphological processes. Distinct F-actin structures in vivo are controlled by a large number of actin-regulatory proteins. These actin regulatory proteins are responsible for the crosslinking, severing, and capping of actin filaments and for site-specific filament growth. Despite a growing availability of high-resolution structures for numerous actin-binding proteins or portions thereof, there is still no direct structural information on their actin-bound conformations. This lab will be utilizing the techniques of small-angle scattering, FTIR, CD, LC-MS with chemical cross-linking and mutagenesis to study of the interaction between actin and its Ca²⁺-regulated binding protein, gelsolin. Molecular modeling of the scattering data collected on complexes of actin and various actin-binding proteins will provide key information on potential domain interfaces or even potential residues essential for the binding, capping or severing activities of actin-binding proteins thereby offering structural insights on actin regulation.

FIGURE 1: Interactions between gelsolin and either monomeric G-actin or filamentous F-actin include filament nucleation, severing and capping activities, all of which require Ca2+. There is evidence for a large conformational change in gelsolin upon binding Ca2+ (Pope et al., 1997, Biochemistry 36: 15848), differing significantly from that of the known EGTA-inactive structure. Additional conformational rearrangements of the Ca2+·gelsolin structure have been inferred for the actin-bound complexes.

Click here for more background on gelsolin:actin project

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