Federal regulators yesterday shut down Mainland Savings Association of Houston, a $1 billion savings and loan that officials said was a victim of bad housing and construction loans, and transfered insured deposits from the failed S&L to a newly created institution.

Officials of the Federal Home Loan Board, the federal agency that regulates the thrift industry, said they closed down the state-chartered, federally insured Mainland because it had a net negative worth, meaning it did not have enough assets to pay all its obligations.

Yesterday's was the first major failure of a Texas financial institution since the dramatic plunge in oil prices hit hard at the already fragile energy economy. The state's once-booming real estate industry also has fallen on hard times -- a reflection both of overbuilding and retrenchment by energy companies.

Many Texas financial institutions, large and small, are major lenders to the oil and gas industry and to real estate developers and will face heavy pressure because their customers will find it difficult to repay their loans on schedule.

Regulators said that on Monday, Mainland despositors whose accounts were federally insured will have access to their money through AllenPark Federal Savings & Loan, a federally chartered institution the bank board set up to take Mainland's healthy assets.

The federal government will provide additional capital to AllenPark, giving it assets that will exceed liabilities by 7 percent, regulators said.

Mainland's loan portfolio will be taken over and sold off by the Federal Savings and Loan Insurance Corp., the division of the bank board that provides federal insurance for deposits up to $100,000, regulators said.

Bank board officials said they do not know the exact amount of deposits that will be transferred to AllenPark, or how much the closing will cost the insurance fund.

"It's going to take all weekend to figure it out," said bank board spokesman Pat McKelvey. "We'll be working 'round the clock."

Mainland is the freshest sign of the growing strain on financial institutions in Texas, California and other fast-growth areas of the country. In these regions, the value of real estate soared during the 1970s and then collapsed just as interest rates began to fall in 1982. Real estate values are continuing to fall as plummeting oil prices sap the Texas economy.

Mainland suffered from another symptom that has caused many savings and loans to fail -- growing too fast. It pushed its loan portfolio from $308 million in Oct. 31, 1983, to over $1 billion by the end of 1985, largely through investments in real estate funded with high-cost deposits such as jumbo certificates and brokered accounts.

To sustain its fast growth, Mainland was offering six-month certificates of deposit yielding 8.55 percent -- the sixth-highest rate in the country, according to 100 Highest Yields, a newsletter. Yields on similar accounts in the Washington area are about 8 percent or less. Bank board officials said that any Mainland depositors who invested in jumbo certificates of deposits higher than $100,000 will not be reimbursed by the insurance fund.

Though not big by Texas standards -- it was the 19th-largest S&L in the state, according to an industry ranking -- Mainland was a billion-dollar institution and among the largest financial institutions ever to fail.

L. William Seidman, chairman of the Federal Deposit Insurance Corp., said in an interview this week that it is unlikely there will be a major commercial bank failure in Texas as a result of the oil-price plunge, but acknowledged that such a failure "is not out of the realm of possibility."

He said that if prices rebound to $15 a barrel, the banking system should weather its problems with no major catastrophes. If the price of oil were to sag below $10 a barrel, the situation would become more serious, he said.

Seidman and the two other federal bank regulators -- the Comptroller of the Currency and the Federal Reserve Board -- told Congress this week that the problems of Texas financial institutions are a crucial reason why the government needs new powers to handle bank failures.

The major rating companies like Standard and Poor's and Moody's -- firms that judge the risk of investing in debt securities issued by corporations -- have downgraded the quality of a number of Texas banks, warning investors of potential problems.

MCorp, the big Dallas-based bank company, announced earlier this week that it expected to report a first-quarter loss of about $120 million because it is building up reserves as a buffer against loan losses it expects will occur among its energy loans.