The law firm signed a letter of intent to move by early 2010 and the building will be renamed K & L Gates Center because the firm will become its largest tenant. The building will also remove the Ariba signs and replace them with K & L Gates signs as part of the transition.

Ariba, based in Sunnyvale, Calif., extended its lease at the building to 2017 earlier this year, but it also cut the amount of space it will use from 10 to five floors.

Kirkpatrick & Lockhart will occupy 13 floors of the building.

The law firm has 235 lawyers and 650 employees in the city, and maintains 21 other offices in the United States, Europe and Asia.