(a) The commission shall be composed of five members as follows: (1) The Auditor of the state, by virtue of his office; (2) the treasurer of the state, by virtue of his office; (3) the State Tax Commissioner, by virtue of his office; and (4) two residents of the state appointed by the Governor by and with the advice and consent of the Senate. Of the two appointed members, one shall be, or shall have been, the mayor of a municipality, and one shall be, or shall have been, a member of a county commission: Provided, That if such mayor or member of a county commission is not presently serving in such position, he shall have served in such position within the six years preceding the term for which such member is to be appointed. No more than one of the members appointed by the Governor may belong to the same political party.

(b) The appointed members of the commission shall serve overlapping terms of four years each and until their respective successors have been appointed and qualified, except for the original appointments, one member shall be appointed for a term of four years and until his successor has been appointed and qualified, one member shall be appointed for two years and until his successor has been appointed and qualified. Each member shall take and subscribe to the oath required by section five, article four of the Constitution of this state.

(c) Vacancies shall be filled by appointment by the Governor for the unexpired term of the member whose office is vacant and such appointment shall be made within sixty days of the occurrence of such vacancy.

(d) No member of the board appointed by the Governor may be removed from office except for official misconduct, incompetency, neglect of duty or gross immorality.