One Equity Partners, a private equity arm of JPMorgan Chase, had reached a deal last year to buy the network, but the agreement fell apart. Lionsgate then bought the network and TVGuide.com two months later for $250 million.
One Equity is paying $123 million for the 49% stake, and the acquisition allows it "under certain circumstances" to buy an additional 1% and become a half-owner.
One Equity's original purchase agreement, reached in December, included investor Allen Shapiro, the former owner of Dick Clark Productions, as a partner.
And under the new arrangement, Shapiro will become chairman of the joint venture. He will co-lead the network's executive committee with Lionsgate CEO Jon Feltheimer. Shapiro had said he would invest heavily in the network, which is in 83 million homes, to build programming quality.
Feltheimer said One Equity "shares our vision of building a dynamic entertainment channel driven by Lionsgate-branded content."
In addition to the TV Guide Network, Lionsgate is a partner in coming pay-TV channel Epix and horror-genre venture FearNet. It is looking to add distribution operations to its production business, which includes AMC's "Mad Men" drama.