You may have seen her previously in supporting roles for 21 Jump Street and The Social Network, but this will be Johnson's first major role. The 23-year old is the daughter of Melanie Griffith and Don Johnson and the granddaughter of Tippi Hedren who starred in Alfred Hitchcock's The Birds.
She will play Anastasia, a 20-year old college student who is coaxed into becoming a young billionaire's sex slave. She is described as being shy and insecure but strong willed and stubborn. She is more tomboyish, pale, and dark haired with blue eyes.
This is probably the closest casting for a book adaptation I have seen in a while, so we will see how this goes.
UPDATE: Charlie Hunnam will play Christian Grey