Weil Gotshal & Manges and US technology firm Fenwick & West are advising on Facebook's $16bn (£9.6bn) acquisition of mobile messaging company WhatsApp.

The deal includes $4bn in cash and approximately $12bn in Facebook shares. WhatsApp's founders and employees will get $3bn (£1.8bn) of the shares as restricted stock that will vest over four years after the deal closes.

Weil is acting for Facebook, fielding a team led by corporate partners Keith Flaum and Jane Ross in Silicon Valley and technology and IP partners Karen Ballack and Barry Fishley. The team was supported by employee benefits, tax and securities lawyers in New York.

Fenwick & West are advising WhatsApp on the sale, led by Mountain View corporate partners Sayre Stevick, Andrew Luh and Shawn Lampron.

Mark Zuckerberg, Facebook founder and CEO said: "WhatsApp is on a path to connect 1 billion people. The services that reach that milestone are all incredibly valuable. I've known Jan (Jan Koum, WhatsApp co-founder and CEO) for a long time and I'm excited to partner with him and his team to make the world more open and connected."

Last year Facebook appointed a new general counsel, promoting vice president and deputy GC Colin Stretch to take up the top legal role.

While deputy GC, Stretch acted as lead negotiator for the company's settlement with the Federal Trade Commission in 2011, and led an appellate victory against the Winklevoss brothers. He has also been the lead in-house lawyer advising the company on new product lines.

He replaced Ted Ullyot, who had been GC since October 2008 before which he was a partner at Kirkland & Ellis.