The Carlyle Group paid $115 million to settle a collusion case Friday, less than a week before it was due for a major hearing on the lawsuit in Boston.

District-based Carlyle was the last of several private equity firms, including Blackstone Group, KKR and TPG, to settle the seven-year-old case. Plaintiffs had alleged that Carlyle and the other private equity firms had colluded, mostly through e-mail, not to bid against one another on takeover targets during the mid-2000s.

Carlyle declined to comment, and a person close to the negotiations said Carlyle settled the case without admitting any wrongdoing on its part.

Six private equity defendants had already agreed to pay $475 million to settle the collusion lawsuit. A group of plaintiffs, suing in federal court, accused Carlyle, Blackstone Group, TPG Capital, KKR and others of agreeing among themselves not to bid against one another in eight corporate takeovers that included theater chain AMC Entertainment, food service firm Aramark and casino operator Harrah’s Entertainment. The plaintiffs were represented by Patrick Coughlin, an experienced class action attorney.

As the lone holdout, Carlyle had taken a high-risk, high-reward strategy. Carlyle faced a legal technicality, known in class action suits as “joint and several,” which makes the remaining single defendant liable for all the damages incurred by the alleged conspirators.

In this case, Carlyle would have been on the hook for $10 billion, which under law can be tripled to $30 billion — or three times the value of Carlyle’s entire firm.

To avoid that kind of worst-case, apocalyptic verdict, all the other defendants settled previously.

As one expert in class-action law put it, the other private equity firms had settled without admitting guilt to reduce the small, but not negligible, risk of a multi-billion jury verdict down the road. One attorney compared it buying health insurance or not.

“If you get sick, you look like you were smart to buy the insurance,” said the attorney. If you don’t get sick, it looks like a waste of money.

Sources familiar with the case, who declined to be identified because they had worried that their statements could be used in court, said Carlyle’s three co-founders, William Conway, Daniel D’Aniello and David Rubenstein, believed they had done nothing wrong and that settling would encourage similar lawsuits.

Carlyle was represented by Latham & Watkins in the case.

Twenty-seven buyouts were originally part of the case. A federal judge in March 2013 threw out claims over alleged collusion before buyouts were announced.