WASHINGTON (AP) _ Here are the key figures in the House Banking Committee's investigation of Lincoln Savings and Loan Association of Irvine, Calif., and a related inquiry into five senators who intervened on its behalf with federal regulators:

CHARLES B. KEATING Jr. - A Phoenix millionaire who, as chairman of a home construction company, American Continental Corp., purchased Lincoln in February 1984 for $51 million and increased its assets from $1.1 billion to $5.5 billion by 1988. Keating waged a fervent five-year campaign against federal thrift regulators who opposed his direct investment of federally insured S&L deposits in real estate ventures. In 1986 and 1987 he contributed a total of $1.3 million to the political causes of five senators who intervened on Lincoln's behalf with officials of the Federal Home Loan Bank Board. Lincoln was seized by the board last April and regulators have filed a $1.1 billion fraud and racketeering suit against Keating.

EDWIN J. GRAY - A former White House official who, as chairman of the bank board from 1983 until July 1987, sought to limit direct investments by thrifts and was sued several times by Keating. In May 1987, Gray deferred action on a recommendation by regulators at the Federal Home Loan Bank in San Francisco that Lincoln be taken over by the government because of what they said were unsafe and unsound lending practices. Gray told the House committee he was summoned to an April 2, 1987, meeting in the office of Sen. Dennis DeConcini, D-Ariz., that was arranged by Sen. Donald W. Reigle, D-Mich. At that meeting and in the presence of three other senators, Gray said DeConcini asked him ''on behalf of their friend and contributor'' at Lincoln to rescind a regulation curbing direct investments by thrifts. Gray subsequently arranged a two-houring meeting April 9, 1987, in DeConcini's office between five senators and San Francisco Home Loan Bank officials then trying to close Lincoln.

M. DANNY WALL - A former banking aide to Sen. Jake Garn, R-Utah, succeeded Gray as chairman of the bank board. Wall has been the chief target of the House Banking Ccommittee's chairman, who last month asked President Bush in a letter to fire him. Wall has said the board did not follow the San Francisco officials' recommendation to seize Lincoln because proof was insufficient to justify the action.

SEN. DENNIS DeCONCINI, D-Ariz. - Hosted in his office April 1987 two meetings between thrift regulators and other senators. DeConcini received $48,100 from Keating and his associates for 1988 re-election campaign but announced two months ago he would return the money. Early this year he called Wall twice and also California state regulators urging approval for Keating to sell Lincoln as an alternative to the government seizing it. DeConcini has denied Gray's account of the April 2 meeting.

SEN. ALAN CRANSTON, D-Calif. - Met with Gray on April 2, 1987, and following week with San Francisco examiners, both in DeConcini's office. Cranston, the No. 2 Democrat in the Senate as the party's whip, also called Wall and California state regulators earlier this year urging approval for Keating to sell Lincoln. For his 1986 re-election campaign, Cranston received $39,000 from Keating and his associates. He also solicited from Keating $850,000 for three voter education projects in California and $85,000 for the California Democratic Party.

SEN. JOHN McCAIN, R-Ariz. - Attended April 2 and April 9 meetings in DeConcini's office; received $112,000 in campaign contributions from Keating and his associates. McCain said earlier this year he was reimbursing American Continental $13,433 for flights he and his family took aboard Keating's corporate planes to and from the Bahamas in 1984-86.

SEN. JOHN GLENN, D-Ohio - Attended April 2 and April 9 meetings in DeConcini's office, where regulators quoted him as telling them to either make a case against Lincoln or ''get off its back.'' A candidate for his party's presidential nomination in 1984, the former astronaut received $34,000 in direct political contributions from Keating and his associates and a political action committee associated with Glenn received another $200,000.

SEN. DONALD W. RIEGLE Jr. - Met several times in 1987 with Keating or his associates and, according to Gray, first told him that he would be summoned to the April 2 meeting in DeConcini's office. Riegle did not attend that meeting but was present at the meeting April 9 with San Francisco regulators. Riegle received a $76,100 from Keating and his associates for his 1988 re-election campaign but announced later he was returning the money.

REP. HENRY B. GONZALEZ, D-Texas - As chairman of the House Banking Committee, has directed a six-hearing investigation into why Lincoln was allowed to stay open for two years after examiners recommended seizing it. For a year, Gonzalez has blamed the size of the S&L crisis on Wall and has attempted to focus the Lincoln hearings on him. Last month he asked President Bush to fire Wall.

MICHAEL PATRIARCA and WILLIAM K. BLACK - Respectively, the principal agent in charge of the San Francisco Bank Board office and its top lawyer. On May 1, 1987, they recommended that Lincoln be seized following a yearlong examination of the thrift. Patriarca and Black were the chief regulators summoned to the April 9, 1987, meeting in DeConcini's office and are now portrayed by House Banking Committee members as the unsung heroes in the Lincoln case.

ROBERT S. BENNETT - A Washington attorney specializing in white collar crime, was hired by the Senate Ethics Committee last week to head an investigation into the role played by the five senators in the Lincoln case. Bennett is a brother of former Education Secretary William J. Bennett, now director of the White House Office of Drug Control Policy.