Mizuho has entered into a $550 million deal with investment bank Greenhill

Mizuho has bought Wall Street investment bank Greenhill & Co in a $550 million deal as one of Japan’s biggest financial institutions tries to accelerate its expansion in the United States.

The Japanese financial services group said it would pay $15 a share for Greenhill, more than double what the U.S. boutique investment bank’s shares closed at on Friday.

Founded by Robert Greenhill nearly three decades ago, Greenhill was among the first M&A advisors to go public. After soaring in the years immediately following its IPO, the group’s shares have languished as Greenhill faced stiff competition from peers and larger investment banks.

Mizuho, ​​which has built up its U.S. investment banking business in recent years, said Greenhill will operate within its existing banking division and will be led by Michal Katz, the current head of banking in the Americas.