A joint venture of MetLife and Norges Bank Investment Management has acquired the One Beacon St. office tower in Boston for $561 million.

The seller was a joint venture of Beacon Capital Partners and insurer Allianz. MetLife will own 52.5 percent of One Beacon St. and be the managing member, while Norges Bank Investment Management will own the remaining 47.5 percent.

The 34-story office tower built in 1973 is approximately 85 percent leased, with more than 1 million square feet of office space. Tenants include JPMorgan Chase Bank, the Massachusetts Housing Finance Agency, the University of Massachusetts and Standard Life Investments Ltd.

In January, MetLife-Norges acquired One Financial Center in Boston along with office properties in Washington, D.C. and San Francisco.

The acquisition brings the joint venture’s real estate portfolio to approximately $2.4 billion. Norges is the world’s largest sovereign wealth fund, with estimated assets under management of $890 billion.