The Securities and Exchange Commission has taken a step toward curbing risk-taking at big Wall Street firms and reducing the influence of credit-rating agencies, two factors that contributed to the financial crisis.

The commission voted Wednesday to back a proposed rule that would make top executives at big firms wait at least three years to be paid at least half of their annual bonuses. The rule would apply to financial firms with $50 billion or more in assets. The Federal Deposit Insurance Corp. advanced the rule last month.

The SEC is also proposing the elimination of a requirement that money-market funds invest only in securities that have credit ratings. The funds would assess the securities themselves.

Both rules were outlined in the financial regulatory law enacted last summer.