Annette Nazareth, a driving force behind new banking regulations for Wall Street's biggest banks, has decided to step down as SEC commissioner and will "pursue other professional opportunities," she said in a letter to President George W. Bush, the letter quoted in the Financial Times.

"Consolidated supervised entity," known as CSE allows the SEC to discuss risks with banks at the holding company level, a model fashioned after British regulations that are "principles-based." It was initiated in the United States in 2004 and is seen as a valuable approach to banking regulation given the current crisis in mortgage securities.

Nazareth was also instrumental in adapting the exchange to the electronic age by introducing Reg NMS, which mandates orders be listed at the lowest price, regardless of where they are published.

Possible successors to fill the two vacancies on the SEC are Elisse Walter and Luis Aguilar. Walter is a regulatory policy executive at the Financial Industry Regulatory Authority. Aguilar is a securities lawyer at McKenna Long & Aldridge.