This is going to sound a bit different from many of the responses, but eaten in large quantities, lettuce has a ton of protein (more than meat PER CALORIE). A great healing source of protein would be comfrey - it contains a great deal of it, in addition to other helpful substances.
We certainly need protein, but our real foods (fruits) contain it as well, and we don't need nearly as much as most "experts" think we do. Beans/lentils that are soaked to start the life and preferably cooked at low heat will contain a lot of usable plant protein.
Dr. Christopher talks at length about the gorilla and where he finds his protein - fruits and vegetables, mainly.