Mo. Rev. Stat. § 386.140: Chairman — his powers.

The chairman of the commission shall designate from time to time, by order entered of record, some member of the commission to act as chairman during the absence or sickness of such chairman appointed by the governor, and during such time the commissioner so appointed shall possess all the powers of the regular chairman. No vacancy in the commission shall impair the right of the remaining commissioners to exercise all the powers of the commission.