Opus Bank, based in Irvine and with about $2.4 billion in total assets, received regulatory approval on its purchase of $143 million of deposits and 10 branches belonging to Pacific Western Bank including three based in San Diego County.

Opus is paying a premium of 2.5 percent on the deposits or about $3.6 million for the deposits. The bank isn’t buying any of the loans.

The three local branches that Opus is picking up are in Carlsbad, El Cajon and La Mesa.

The additional branches bring Opus’ total number in the county to five. It opened offices in La Jolla and Del Mar earlier this year.

The seven other branches are in Encino, Monrovia, South Pasadena and Westwood in Los Angeles County; Chino and Twentynine Palms in San Bernardino County; and La Quinta in Riverside County.

PacWest Bancorp, the parent company to Pacific Western Bank and based in Los Angeles, said the transaction would improve its efficiencies and profits.

Opus and Pacific Western said they would work closely together to assure a smooth transition for clients and employees. Opus said it expects to open the 10 branches under its name Sept. 24.