E*Trade Financial Corp, another discount broker, said in July that it would buy online brokerage OptionsHouse for $725 million, while Ally Financial Inc purchased TradeKing Group for about $275 million a month earlier. In a connected deal, Toronto-Dominion Bank, TD Ameritrade's biggest shareholder, said on Monday it had agreed to buy Scottrade's banking business for $1.3 billion as it continues to ramp up its expansion in the United States. TD Ameritrade's acquisition of Scottrade combines two of the United States' "big five brokerages", the others being Charles Schwab, Fidelity Investments and E-Trade, and would leave only four major brokers operating in the marketplace. "I think that the authorities in the United States are unlikely to let this pass without a pretty close look," said John Briggs, an antitrust attorney with the law firm Axinn, Veltrop & Harkrider.