John Mack, the chairman of Morgan Stanley, will step down from his post and leave the board of directors at the end of this year, the Wall Street investment bank announced on Thursday. He will be replaced by the bank\'s chief executive James Gorman, who will assume both roles effective January 1, the bank said in a statement.\"Working with the remarkable people of Morgan Stanley has enriched my life for more than three decades, and helping to lead this great firm, most recently as Chairman, was the greatest honor of my career,\" Mack said. Mack, who was Morgan Stanley\'s chief executive until 2009, is a Wall Street veteran who helped the bank survive the 2008 financial crisis at a time when many of its rivals went bankrupt or lost their independence.He helped engineer the deal in which Japanese banking giant Mitsubishi UFJ acquired a stake in Morgan Stanley in September 2008, giving the Wall Street bank a badly needed capital injection amid the crisis. Mitsubishi UFJ currently owns 22.4 percent of Morgan Stanley.Shares of Morgan Stanley surged 4.7 percent in midday trading, outpacing gains in other US financial stocks.