Mo. Rev. Stat. § 226.120

The members of the commission shall elect a member as chairman and another vice chairman, each of whom shall hold such office for a term prescribed by the commission. Four members of the commission shall constitute a quorum for the transaction of business and for the exercise of any of the powers or the discharge of any of the duties authorized or imposed by law. The commission shall meet at least once each month and at such other times, and at such places within the state, as the commission shall determine. The chairman or, in the event of his inability to act, the vice chairman may call special meetings of the commission upon notice to members.