Add ERK phosphorylation of Sos (negative feedback)
Add ERK phosphorylation of Sos (negative feedback)

sorgerlab/ras_model,jmuhlich/rasmodel,johnbachman/rasmodel,jmuhlich/ras_model,jmuhlich/ras_model,subkar/rasmodel,johnbachman/ras_model,sorgerlab/rasmodel,johnbachman/rasmodel,sorgerlab/ras_model,jmuhlich/rasmodel,johnbachman/ras_model,sorgerlab/rasmodel