Two Wall Street titans and Pittsburgh’s two biggest law firms are among the six Am Law 50 firms behind two federal suits filed Monday that aim to salvage Japanese steelmaker Nippon Steel Corp.’s proposed acquisition of Pittsburgh-based U.S. Steel.

Attorneys from K&L Gates, Milbank, Reed Smith, Ropes and Gray, Mayer Brown and Wachtell Lipton Rosen & Katz all have a role in two separate lawsuits the steel-makers filed in the U.S. District Court for the Western District of Pennsylvania and the U.S. Court of Appeals for the District of Columbia Circuit.