In Vitro Dissection of the Membrane and RNP Binding Activities of Influenza Virus M1 Protein

Abstract

Spontaneous proteolysis of influenza virus M1 protein during crystallisation has defined an N-terminal domain of amino acids 1–164. Full-length M1, the N-terminal domain, and the C-terminal part of M1 (residues 165–252) were produced in Escherichia coli. In vitro tests showed that only full-length M1 and its N-terminal domain bind to negatively charged liposomes and that only full-length M1 and its C-terminal part bind to RNP. However, only full-length M1 had transcription inhibition activity. Several independent experimental approaches indicate that in vitro transcription inhibition occurs through polymerisation/aggregation of M1 onto RNP, or of M1 onto M1 already bound to RNP, rather than by binding to a specific active site on the nucleoprotein or the polymerase. The structure/function of influenza virus M1 will be compared with that of the Ebola virus matrix protein, VP40.