When the Federal Trade Commission began investigating Apple (AAPL) and Google's (GOOG) overlapping boards, it was just a matter of time before they got to Arthur Levinson.

Levinson, the former chairman and CEO of Genentech (DNA), joined Apple's board in 2000 and Google's in 2004.

Since then, the two companies have become increasingly competitive, and last May the FTC began an inquiry into whether the presence of Levinson and Google CEO Eric Schmidt on both boards violated the interlocking directorates provision of the Clayton Antitrust Act.

Schmidt resigned from Apple's board in July. Google announced on Monday that Levinson was resigning from its board, effective immediately.

No reason was given, although Schmidt did issue a statement: More