Dimerization of human drebrin-like protein governs its biological activity

Abstract

Drebrin-like protein (DBNL) is a multidomain F-actin binding protein, which also interacts with other molecules within different intracellular pathways. Here, we present quantitative measurements on size and conformation of human DBNL. Using dual focus fluorescence correlation spectroscopy, we determined the hydrodynamic radius of DBNL monomer. Native gel electrophoresis and dual color fluorescence cross-correlation spectroscopy show that both endogenous and recombinant DBNL exist as dimer under physiological conditions. We demonstrate that C-terminal truncations of DBNL downstream of the coiled-coil domain result in its oligomerization at nanomolar concentration. In contrast, the ADF-H domain alone is a monomer, which displays a concentration-dependent self-assembly. In vivo FLIM-FRET imaging shows that the presence of only actin-binding domains is not sufficient for DBNL to localize properly at actin filament inside the cell. In summary, our work provides a detailed insight on structure-function relationship of human drebrin-like protein.