Dynamic Scaling Analysis of Molecular Motion within the LAT:Grb2:SOS Protein Network on Membranes.

Biochemical signaling pathways often involve proteins with multiple, modular interaction domains. Signaling activates binding sites, such as by tyrosine phosphorylation, which enables protein recruitment and growth of networked protein assemblies. Although widely observed, the physical properties of the assemblies, as well as the mechanisms by which they function, remain largely unknown. Here we examine molecular mobility within LAT:Grb2:SOS assemblies on supported membranes by single-molecule tracking. Trajectory analysis reveals a discrete temporal transition to subdiffusive motion below a characteristic timescale, indicating that the LAT:Grb2:SOS assembly has the dynamical structure of a loosely entangled polymer. Such dynamical analysis is also applicable in living cells, where it offers another dimension on the characteristics of cellular signaling assemblies.