Daniel Akerson will take over as chairman and chief executive of General Motors come Sept. 1, when Ed Whitacre steps down.

The news of Whitacre’s departure was made public this morning, when GM announced second-quarter earnings results — $1.3 billion of profit on $33.1 billion of sales.

Whitacre joined GM in December, replacing Fritz Henderson. Whitacre “simplified the organization, reshaped the company's vision, put the right people in place, and brought renewed energy and optimism to GM,” said Pat Russo, lead director on the GM board.

Akerson, meanwhile, joined the GM board in July 2009. He’s managing director of the Carlyle Group buyout fund. Previously, he served as chairman and CEO of XO Communications and Nextel Communications.