Atomistic models from orientation and distance constraints using EPR of a bifunctional spin label (Biophysical Journal)

We have used high-resolution orientation and distance measurements derived from electron paramagnetic resonance (EPR) of a bifunctional spin label (BSL) to build and refine atomistic models of protein structure. We demonstrate this approach by investigating the effects of nucleotide binding on the structure of myosin`s catalytic domain (CD), while myosin is in complex with actin. Constraints for orientation of individual helices were obtained in a previous study from continuous-wave EPR (CW-EPR) of myosin labeled at specific sites with BSL in oriented muscle fibers.