Mo. Rev. Stat. § 86.310

For the purpose of meeting disbursements for benefits and other payments there may be kept available cash not exceeding ten percent of the total assets of the retirement system on deposit in one or more banks or trust companies in said cities, organized under the laws of the state of Missouri, or of the United States; provided, that the amount on deposit in any one bank or trust company shall not exceed twenty-five percent of the paid-up capital and surplus of such bank or trust company.