(1) All bonds or other obligations purchased according to section 8 shall be placed in the hands of the state treasurer, who is hereby designated as custodian of the bonds or other obligations, and it shall be his or her duty to collect the principal and the interest on the bonds or other obligations as they become due and payable, and deposit the principal and interest when collected into the retirement system’s funds provided for bonds or other obligations. The administrative board may sell any of the bonds or other obligations upon like resolution, and the proceeds of the bonds or other obligations shall be paid by the purchaser to the state treasurer upon delivery to him or her of those bonds or other obligations by the state treasurer.

  (2) The state treasurer shall be the custodian of all other funds of the retirement system and all disbursements shall be paid by the state treasurer upon vouchers authorized by the retirement board and bearing the signature of the authorized officer of the retirement board. The state treasurer shall give a separate and additional bond in an amount as may be established by the retirement board in the sum of not to exceed $100,000.00 which bond shall be approved by the attorney general and shall be conditioned for the faithful performance of his or her duties as custodian of the funds of the retirement system. The cost of the bond shall be paid out of the expense fund of the retirement board. The bond shall be deposited with the secretary of state and kept in his or her office.

  (3) The state treasurer is hereby authorized and directed to deposit any portion of the funds of the retirement system not needed for immediate use in the same manner and subject to all the provisions of law with respect to the deposit of state funds by the state treasurer, and all interest earned on retirement system’s funds as may be deposited by the state treasurer under this act shall be collected by him or her and placed to the credit of the retirement fund.