SJ Berwin and Freshfields Bruckhaus Deringer have acted on the $755m (£490m) sale of UK private equity group Pantheon, a deal which has also handed roles to a trio of US firms.

Freshfields advised acquisitive US money-holding company Affiliated Managers Group (AMG) on its proposed purchase of Pantheon – a private equity fund-of-funds manager – from Russell Investments.

SJ Berwin took the lead role for Pantheon on the deal, which is expected to close in the second quarter and see AMG pay the approximately $755m in a cash transaction, although AMG said the sale price could increase over a five-year period based on the growth of Pantheon's business.

City-based M&A specialist Rob Day was the lead partner for SJ Berwin on the deal, heading up a team that included tax partner Dominic Adams, funds partner Duncan Woollard and regulatory partner Tamasin Little.

City-based corporate partner Matthew Cosans led the Freshfields team which also included tax partner Colin Hargreaves and financial institutions partner Mark Kalderon, who is currently seconded to Freshfields' Hong Kong office.

The deal also handed roles to two of SJ Berwin's US allies – Boston-based private equity heavyweight Goodwin Procter and New York's Paul Weiss Rifkind Wharton & Garrison. Goodwin took the US mandate for Pantheon while Paul Weiss advised AMG alongside Freshfields.

Meanwhile, Skadden Arps Slate Meagher & Flom advised Russell Investments, the subsidiary of Northwestern Mutual Life Insurance Company that currently owns the stake.

Boston-based financial services partner and banking group head Tom LaFond and New York-based tax partner Bill Weiss advised from SJ Berwin best friend firm Goodwin.