By Steve Keating

LONDON (Reuters) - It is the Hollywood-styled boxing tale begging for a cinematic release.

A young fighter growing up in Flint, Michigan, which according to a 2011 FBI report are some of the most dangerous streets in America, finds purpose and success in the ring.

But this 'Rocky' story comes with a twist.

The boxer is Claressa Shields, a brash 17-year-old high school student, not a journeyman underdog and the ring is an Olympic one in London where for the first time women will fight for a gold medal.

The rest of the script, however, rings with familiarity.

A Rust Belt relic beaten down by the collapse of the auto industry, Flint had the second-highest murder rate in the United States and the highest rates of aggravated assault, burglary and arson in 2011.

Few in the city have been left untouched by the violence and the headlines seldom bring good news.

Until Monday. When Shields put away Sweden's twice-former world champion Anna Laurell with a ferocious fourth round flurry to take another step towards what she constantly refers to as "My gold medal".

"I box for a lot of reasons," said Shields. "To show you can come from a real small city where you're not really acknowledged and you can become something.

"I fight because I feel it is the best thing I am good at winning at. I want to win I want to be successful.

"I've lost so many of my friends...the last two summers, I had a total of four friends (killed) I was never able to go to their funerals. Gun violence," sighed Shields with a shrug.

"Anthony Ivy was a friend of mine, he was in that seven day shooting up in Flint, seven days, seven murders he was in that.

"There's nothing I can do about it. I just pray to God to protect my family to protect my friends and I pray for Flint especially."

SPORTING CREDIBILITY

The New Yorker, Time, Sports Illustrated and a line of television crews and interviewers beat a path to Flint during the buildup to the London Games to get an audience with the fighter they believe is going to put women's boxing on the sporting map.

It is something that Laila Ali, Jaqui Frazier, and Freeda Foreman, the daughters of three former-heavyweight greats were unable to do in the professional ranks, but the Olympic stage lends women's boxing credibility and it will be up to the charismatic Shields to help sell it to a skeptic public.

The teenager may also leave London as the savior of a crumbling U.S. boxing program.

Americans have won more boxing gold than any nation but have seen their production in the ring reduced to a single bronze in Beijing and for the first time could face the humiliation of leaving an Olympics without a man reaching the medal podium.

Cast from the same showman's mould as Ali, Shields exudes a brash, cockiness and a 27-1 record to back up her talk.

Quick and powerful, U.S. coaches describe the teenager as a throwback, her raw aggression more reminiscent of professional boxing than amateur.

"She has some bad intentions in her punches," said U.S. coach Charles Leverette. "If she lands it clean someone is going somewhere. She gives everything she has in the ring."

Shields' father, who served a seven year prison term for breaking and entering, encouraged his daughter to pursue boxing after he was released.

Clarence Shields was not in London on Monday but continues to inspire his daughter with little stories like one he told her before her opening bout.

"My dad loves that I box, I talk to him every day," said Shields.

"He tells me these little stories like, do you remember when you were little and I took you to the store to get a bicycle and a girl took the bicycle from you and you were too little to fight her.

"Well, that's the girl you're fighting that girl tonight. You're big enough now to beat her you better go get your bicycle back.

"Ain't nobody taking nothing from me."

(Editing by Greg Stutchbury)