Identification of the Protease-Binding Domain in the N-Terminal Region of Influenza Virus A Matrix Protein M1

A region responsible for protease binding by influenza virus A matrix protein M1 was identified. Trypsin binding was observed with the N-proximal 9-kDa fragment obtained by cleaving M1 with formic acid. The binding was inhibited by monoclonal antibodies (mAb) to region 46–70 of M1 and by an antiserum to region 21–45, whereas mAb to the middle and C-terminal regions had no effect. Thus, the protease-binding domain was mapped to the N-terminal part of M1.