King Street Properties broke ground today on its $45.5 million life science building in Lexington.

Rep. Jay Kaufman (D-Lexington), Lexington Chairman of the Board of Selectmen Joe Pato, Massachusetts Life Sciences Center CEO Travis McCready and MassBIO Executive Vice President Sarah MacDonald attended a ceremony at the site, known as The Hartwell Innovation Campus (THINC), located at 115 Hartwell Ave.

The 91,000-square-foot, LEED-certified building will be the fourth building on the campus, and will house 300 employees, as well as support 350 construction jobs during construction. As part of the building development, King Street is planning a single-story café at the center of the campus designed to support the company’s food truck program, provide coffee service and act as a social hub for THINC. The project is scheduled to be completed by the end of 2016 and is available for lease through JLL as King Street’s leasing agent.

“The new 115 Hartwell Ave. development project is the first ever speculative ground-up laboratory construction in the suburbs of Boston,” Thomas Ragno, founder and principal of King Street, said in a statement. “Our goal is to create an urban atmosphere in a suburban campus environment, providing amenities that can be found in urban centers and creating settings that foster collaboration and innovation.”

Cambridge-based King Street is the largest privately held owner of life science real estate in the Greater Boston area.