Lt. Gov. Tina Smith resigned Thursday as chairwoman of the board of directors for Mayo Clinic’s $5.6 billion expansion, known as Destination Medical Center (DMC).

Smith, who has served as the board’s chairwoman since its inception in 2013, submitted her resignation in letters to Gov. Mark Dayton and DMC directors. Smith was appointed by Dayton earlier this month to take over the U.S. Senate seat held by Al Franken.

Former Minneapolis Mayor R.T. Rybak, the vice chairman, will take over as interim chairman.

The DMC project, which blends private investment with public money to fuel growth over 20 years, originally was pitched as a needed step to keep Mayo competitive with other world-class medical centers.

Mayo will expand its campus and extend its medical know-how with $3.5 billion in investments over the course of DMC’s life span, while private investors are expected to add another $2.1 billion in residential, retail and commercial investments. About $585 million in tax money will build the public infrastructure necessary to tie it all together.

The plan calls for adding more than 30,000 jobs in Rochester, adding tens of thousands of people to the city’s population and generating billions in tax revenue.

Some 14 construction projects worth an estimated $736.8 million are either planned or in the works or have recently been completed in the roughly 550-acre zone delineated for renovations and new construction.

“I am proud of the work we accomplished together, and am confident that under your leadership DMC can continue to move ahead,” Smith wrote in her letter to the board of directors. “During the past four years we have made significant progress. …

“These accomplishments are a testament to the leadership of this board and the hard work and ingenuity of the people of Rochester who made this city a global health care destination.”

In a statement Thursday, Dayton called Smith a “tremendous champion” for the DMC expansion, adding that she “has been crucial to the project’s successes.”