Virtu Financial Inc.'s bid to become one of the biggest companies in the high-frequency trading market got one step closer in late April with its proposed $1.4 billion all-cash acquisition of electronic trading rival KCG Holdings Inc.

The deal, announced on April 20 and expected to close in the third quarter, will result in New York-based Virtu controlling about 20 percent of the U.S. equity trading market. Paul, Weiss, Rifkind Wharton & Garrison is advising longtime client Virtu on the merger, which will unite two of the country's largest electronic trading firms in a time of reduced market volatility. The transaction has also yielded roles for a half-dozen Am Law 100 firms.

Back in 2008, Virtu was founded by Vincent Viola, a New York Law School graduate and former chair of the New York Mercantile Exchange. In launching Virtu, Viola recruited Paul Weiss deputy corporate chair Douglas Cifu to serve as Virtu's president and COO. Viola and Cifu met in 2004 when Paul Weiss and Cifu advised private equity firm General Atlantic LLC on its $135 million acquisition of a 10 percent stake in NYMEX Holdings Inc., owner of the New York Mercantile Exchange.