DETROIT (Reuters) — Billionaire Kirk Kerkorian’s Tracinda Corp. investment firm yesterday said it had sold $462 million of stock in General Motors Corp this week, cutting its stake in the automaker to 7.4 percent from 9.9 percent.The news sent GM stock plummeting. Shares lost more than five percent in mid-afternoon trade on the New York Stock Exchange — the largest one-day fall in percentage terms since October 6, when the automaker said it would not seek an alliance with Renault-Nissan.

Since Friday, GM’s shares have dropped about ten percent. The stock’s five percent decline on Wednesday was the biggest drag on the Dow Jones industrial average.

News of Kerkorian’s GM sale came on the same day he announced a tender offer for $825 million of stock in MGM Mirage Inc. that would raise his stake to almost 62 percent of the hotel and casino operator.

Kerkorian’s dual moves touched off speculation that the billionaire investor, who has a history of trading corporate assets in Las Vegas, Hollywood and Detroit, could be steering away from a protracted fight for control of GM’s board.

“It signals that he pretty much is going to go quietly into the night,” said Kevin Reale, an automotive analyst at AMR Research.

In a US regulatory filing, Tracinda said it had agreed yesterday to sell 14 million GM common shares in a private transaction for $33 per share.

Kerkorian’s associate Jerry York resigned from GM’s board on October 6 in a dispute over board oversight and strategy triggered by GM’s decision not to pursue the alliance with Renault-Nissan he had attempted to broker on Kerkorian’s behalf.