Projects

Regulation of Enzyme Activity and Function via Filamentation

In 2010, our lab was one of the first labs to report on a new mechanism of regulating enzyme activity. This newly discovered mechanism involves the polymerization of filaments into linear or helical polymers. In the case of the enzyme SgrAI, filamentation activates its DNA cleavage activity 200-1000 fold and also intriguingly alters its DNA sequence specificity such that it cleaves many additional targets. Our work show the structural origins of enzymatic activation, using both x-ray crystallography and cryo-electron microscopy. Computational modeling of the reaction pathway and global fitting to FRET kinetic data, suggest that this mechanism has advantages over more conventional mechanisms in rapid activation of SgrAI and selectively towards invading phage DNA, thereby protecting its host.

The lab is now investigating the role of enzyme filamentation in other enzymes. To date, nearly thirty enzymes have been confirmed to form filaments, though in most cases the effect on enzyme activity and biological function is not known. Further, more than 100 enzymes form self-assemblies in cells, which may result from enzyme filamentation. The biological roles of these self-assemblies are largely unknown. These enzymes play roles in diverse biological pathways, including metabolism, defense, and signaling, among others, and come from organisms representing all branches of life indicating an important evolutionary function.

To the right are two slides: the top slide shows the known noncytoskeletal filamentous enzymes, and the bottom slide shows the many enzymes that form membrane-less self-assemblies in cells.

Several important questions remain:

(1) What function does enzyme filamentation serve in regulating enzyme activity and/or its biological function

(2) How are the cellular self-assemblies related to enzyme filamentation?