Getco on Wednesday said it plans to expand its New York Stock Exchange floor-trading business as part of a long-range plan by the Chicago-based trading firm to build a client base of issuers and financial institutions.

Closely-held Getco, best known as an electronic market-maker, will handle about one-third of daily stock trade at the Big Board after agreeing to acquire Bank of America's NYSE floor business, supervising some of the most widely followed US stocks.