Host IQGAP1 and Ebola virus VP40 interactions facilitate virus-like particle egress.

We have identified host IQGAP1 as an interacting partner for Ebola virus (EBOV) VP40, and its expression is required for EBOV VP40 virus-like particle (VLP) budding. IQGAP1 is involved in actin cytoskeletal remodeling during cell migration and formation of filopodia. The physical interaction and the functional requirement for IQGAP1 in EBOV VP40 VLP egress link virus budding to the cytoskeletal remodeling machinery. Consequently, this interaction represents a novel target for development of therapeutics to block budding and transmission of filoviruses.

A single-molecule analysis reveals morphological targets for cellulase synergy.

The mechanisms of enzyme activity on solid substrates are not well understood. Unlike enzyme catalysis in aqueous solutions, enzyme activity on surfaces is complicated by adsorption steps and structural heterogeneities that make enzyme-substrate interactions difficult to characterize. Cellulase enzymes, which catalyze the depolymerization of cellulose, show binding specificities for different cellulose surface morphologies, but the influence of these specificities on the activity of multienzyme mixtures has remained unclear. We developed a metric to quantify binding-target arrangements determined by photoactivated localization microscopy, and we used that metric to show that combinations of cellulases designed to bind within similar but nonidentical morphologies can have synergistic activity. This phenomenon cannot be explained with the binary crystalline or amorphous classifications commonly used to characterize cellulase-binding targets. Our results reveal a strategy for improving the activity of cellulolytic mixtures and demonstrate a versatile method for investigating protein organization on heterogeneous surfaces.