Melanie Griffith, '50 Shades' fans react to casting of Dakota Johnson, Charlie Hunnam

Dakota Johnson has been tapped to play Anastasia Steele in the film adaptation of "50 Shades of Grey." Charlie Hunnam will play the title character, Christian Grey.

Author E.L. James tweeted the news Monday.

I am delighted to let you know that the lovely Dakota Johnson has agreed to be our Anastasia in the film adaptation of Fifty Shades of Grey.

— E L James (@E_L_James) September 2, 2013

Johnson, daughter of Don Johnson and Melanie Griffith, is best known for her work on the Fox sitcom "Ben & Kate." She has also held supporting roles in "The Social Network," "The Five-Year Engagement" and "21 Jump Street."

This is Johnson's first major big-screen role, after being selected over rumored candidates Emma Watson, Alexis Bledel and Analeigh Tipton.

In the trilogy, Anastasia Steele is the woman that gets involved in a sexual affair with the title character, Christian Grey.

James also announced that Hunnam was cast to play the title role.

The gorgeous and talented Charlie Hunnam will be Christian Grey in the film adaptation of Fifty Shades of Grey.

— E L James (@E_L_James) September 2, 2013

Hunnam, 33, is best known as Jax Teller in "Sons of Anarchy," the beloved FX motorcycle club drama. The two actors had to do a "chemistry read" before the casting to convince producers they had enough heat between them to pull off the story.

The reaction to Hunnam and Johnson's casting has been mixed.

Johnson's proud mother tweeted her excitement over the role.

My beautiful child Dakota has been chosen to play Anna Steele in 50 Shades!!! Look out world! Here she comes!!! #proudmama

— Melanie Griffith (@MelanieGriffith) September 2, 2013

But the rest of the Internet was not as sure. The bestselling novel has scores of female fans personally attached to the storyline. Given that Johnson is relatively unknown, fans have cast speculation as to whether she can live up to their expectations.

For Christian Grey, the reaction is more difficult to pinpoint. Physically, Hunnam fits the part. He is older than Grey in the books, who is in his late-20s. Some fans had already slated their Grey with Matt Bomer or Ian Somerhalder, and were upset to see that Hunnam was the choice.

That in mind, bigger names for each character might have drawn more buzz for the film. Either way, though, James' books have an enormous fan base that are likely to see the movie regardless of the actors cast.