Determination of a molecular shape for netrin-4 from hydrodynamic and small angle X-ray scattering measurements.

As part of a continuing investigation of netrins, an emerging class of extracellular matrix proteins that are involved in axon guidance activity, we have used dynamic light scattering (DLS) and small angle X-ray scattering to investigate the solution conformation of a truncated version of netrin-4 (Δnetrin-4) that lacks the C-terminal portion. The protein is characterized by a hydrodynamic (Stokes) radius (r(H)) of 4.60 (±0.20) nm, a radius of gyration (r(G)) of 4.42 (±0.20) nm and a maximum particle dimension (D(max)) of 16nm. More detailed ab initio modeling of the SAXS data indicates an extended rod like conformation for Δnetrin-4 in solution-a concept supported by the excellent agreement observed between experimental parameter estimates and those calculated for the ab initio models for Δnetrin-4 by the HYDROPRO program.