PROBLEM TO BE SOLVED: To provide a method for extending a serum half-life and a method for using the same.SOLUTION: According to the present invention, there is provided a polypeptide in which a deimmunized serum binding protein portion is a variant of a wild-type albumin-binding domain (ABD) of streptococcal protein G having a specific amino acid sequence. As the polypeptide comprises a polypeptide portion of the deimmunized serum-binding domain, which can bind serum protein by the variant of ABD, the polypeptide is allowed to have an extended serum half-life.SELECTED DRAWING: Figure 66【課題】血清半減期を延長する方法と使用法の提供。【解決手段】脱免疫化アルブミン結合タンパク質の部分が、特定の配列のアミノ酸配列を有するストレプトコッカスのプロテインGの野生型アルブミン結合ドメイン(ABD)の変異体であり、前記変異体ABDにより、血清タンパク質に結合できる脱免疫化血清結合タンパク質のポリペプチド部分を含むことで、血清半減期が延長されたポリペプチド。【選択図】図66