Shopping centers in the new town of Reston may soon provide pension payments for retirees whose pension funds are invested in what could become an increasingly important institutional investment - real estate.

A group of pension funds managed in California is now negotiating to buy three shopping centers in Reston, at Lake Ann, Hunter's Woods and Tall Oaks, along with 18 other income properties in the community, from Gulf Oil Co., which is divesting its interest in Reston and getting out of the real estate business.

The buying group is known as CB Institutional Fund III, and is managed by Coldwell-Banker, the big real estate firm. After making two smaller real estate deals, the fund have pooled their money and given Coldwell-Banker $55 million to buy properties. Coldwell-Banker will manage the buildings.

The Coldwell-Banker fund is one of less than a dozen such plans in the country and represents a fundamental change in the way pension funds invest in real estate.

Institutional investors have been in real estate before, but only as passive investors, making mortage loans to property owners, and collecting interest on its investment just like a bank holding a mortgage.

But now pensions are taking equity positions in real estate, accepting the risks of ownership in return for higher income.Like other real estate buyers, the pension funds will use their own money only for a down payment on the Reston properties, getting a mortgage from a lender.

The result is a leveraged investment. Instead of holding $55 million worth of mortgages, CB Institutional Fund III will be able to buy real estate worth several times that much.

Pension fund specialists say real estate equities could become a major new investment vehicle.