Vestar Capital Partners has closed a $364 million deal for Institutional Shareholder Services Inc. 

The target provides corporate governance services to the financial community, supplying things like proxy research and analysis, proxy voting and distribution services. The seller was MSCI Inc. (NYSE: MSCI), which provides investor tools.

The deal was originally announced in March.  

Vestar, a New York private equity firm, focuses on investments between $250 million and $1 billion in enterprise value. The firm invests in companies in the financial services, information services, consumer health care and digital media industries. In August, Vestar bought a majority stake in American Roland Food Corp., which imports specialty food products. 

Simpson Thacher & Barlett LLP acted as Vestar's legal counsel. Morgan Stanley was MSCI's financial adviser, while Davis Polk & Wardwell LLP provided legal advice.

For more on shareholder activism in the middle market, see "The Buyside: Activist Investors Dig Into Mid Market."