The Art Market Monitor‘s Marion Maneker reports that Marc Porter has resigned from his post as chairman of Christie’s Americas and will leave the company by the end of the year. He will join rival auction house Sotheby’s, as confirmed in a tweet by the Wall Street Journal‘s Kelly Crow.

“@Sothebys CEO confirms Marc Porter hire: ‘He will take on a role that will empower him to bring his decades of global experience’ in art,'” Crow tweeted on December 7 at 7:52 AM.

Christie’s has also confirmed Porter’s departure. “We would like to thank Marc for his exceptional contribution to Christie’s over many years which has seen him lead the New York Trusts and Estates Department, the President’s Office and the Chairman’s Office of the Americas,” Jussi Pylkkanen, Christie’s Global President said in a statement.

“He will take on a role that will empower him to bring his decades of global experience in fine art to bear on the needs of our most valuable clients around the world,” said Tad Smith, Sotheby’s chief executive.

Pylkkanen noted that Porter’s responsibilities will be assumed by Brook Hazelton, president of Christie’s Americas.

Porter has been with the blue-chip auction house since 1990, when he joined as International Managing Director. In 2009, he was appointed to his recently-vacated post, in which he executed high-profile sales like the $157 million auction of Elizabeth Taylor’s jewelry (which was more recently the news again) and the Andy Warhol online sale.

Porter, who is known in the field as a rainmaker with many exclusive connections, is a major get for Sotheby’s. The shakeup comes after a round of voluntary buyouts at the auction house, offered to employees as a means of cutting costs.