Downtown L.A. asset manager TCW Group Inc. has acquired Beverly Hills private equity firm Craton Equity Partners, TCW announced Monday.

Craton invests in clean technology companies and bills itself as a socially responsible investor. That was part of the attraction for TCW, said Jess Ravich, a TCW managing director who oversees the firm’s alternative investment products.

“The acquisition of Craton Equity further expands our alternative asset management platform at a time when institutional investors are increasingly issuing mandates for socially responsible investing,” Ravich said in a press release.

Terms of the deal were not disclosed. Craton manages $242 million, a sum that won’t materially affect TCW’s $130 billion in assets under management.

Bob McDonald and Tom Soto, Craton’s founders and managing partners, will become managing directors. The rest of the Craton team will also join TCW, according to the release.