[Mortgage loan sales to federal national mortgage

association authorized.] Notwithstanding any other provision of law, any institution, including a bank, trust company, building and loan association, insurance company or other banking, building or insuring organization, organized under the laws of this state, which has as one of its principal purposes the making or purchasing of loans secured by real estate mortgages, is authorized to sell such mortgage loans to the federal national mortgage association, a corporation chartered by an act of congress, or any successor thereof, and in connection therewith to make payments of any capital contributions, required pursuant to law, in the nature of subscriptions for stock of the federal national mortgage association or any successor thereof, to receive stock evidencing such capital contributions and to hold or dispose of such stock.