Houston-based Prosperity Bancshares is acquiring San Antonio-based Southwest Bancshares for $268.9 million..The deal is expected to close in the first quarter of next year. Prosperity Bancshares is the parent company of Prosperity Bank. Southwest Bancshares is the holding company of Texas Partners Bank. Prosperity Bancshares had $38.4 billion in assets as of June 30, and operates 283 branches in Texas and Oklahoma. Following the acquisition, Prosperity Bancshares will have 10 branches in the San Antonio area, and expand into Kerrville and Bandera, Texas. The $2.4 billion Texas Partners Bank has 11 branches across Central Texas, including in San Antonio, Austin and the Hill Country. As of June 30, the bank also reported $1.9 billion in loans and $2.1 billion in deposits.Texas Partners Interim Chair Brent Given will join Prosperity Bank as San Antonio area chair. Texas Partners Chief Operating Officer Tom Moreno will take a senior management position, while additional Texas Partners will keep leadership positions. Southwest Bancshares President and CEO Gene Dawson Jr. will join the Prosperity Bank board. Southwest was advised by Little Rock-based financial firm Stephens Inc. and Austin-based law firm Fenimore Kay Harrison LLP, while Prosperity received legal counsel from New York City-based Wachtell, Lipton, Rosen & Katz.