Simpson Thacher & Bartlett is representing U.S. buyout firm Kohlberg Kravis Roberts & Co. on a $4.5 billion acquisition of Japanese auto parts maker Calsonic Kansei Corp.

In a rare multibillion-dollar inbound private equity deal announced on Tuesday, KKR has agreed to buy a 41 percent stake in Calsonic Kansei from Nissan Motor and the remainder from the public market through a tender offer.