Photo courtesy of The Davis Cos.

A New York investor has joined the ownership of two Davis Cos. properties, including a Wellington Circle lab conversion that recently secured its first life science tenant.

Partners Group formed a joint venture with Boston-based Davis Cos. on One Cabot in Medford and 1025-1075 Main St. in Waltham, a deal that values the two properties at $260 million.

The Davis Cos. bought the One Cabot in 2015 for $53 million and attracted new tenants including Amazon to the 309,000-square-foot complex across from the MBTA’s Wellington Orange Line and bus station.

Last summer, the firm revealed plans to convert office space in the building into lab-ready suites as leases expire. The first life science tenant to commit is Cambridge-based Torus Biosystems, which raised $25 million in series A venture capital financing in 2021.

“The benefit of this building is because of the way it lays out and the existing infrastructure, it really lends itself to be converted [to labs] on almost a suite-by-suite basis,” Davis Cos. Chief Investment Officer Quentin Reynolds said of the former Bank of America data center.

Torus, which specializes in infectious disease diagnostics, will occupy 23,570 square feet at One Cabot. The Davis Cos. is in the midst of a phased life science conversion and plans to offer two additional 26,000-square-foot speculative lab suites that will become available in eight and 15 months.

In Waltham, Partners Group joined the ownership of Cityside, a 311,000-square-foot office complex at 1025-1075 Main St.

Davis Cos. has secured 193,000 square feet of leases since acquiring the property in 2015 for $52.5 million.