The influenza M2 H+ channel enables the concomitant acidification of the viral lumen upon endosomic internalization. This process is critical to the viral infectivity cycle, demonstrated by the fact that M2 is one of only two targets for anti-flu agents. However, aminoadamantyls that block the M2 channel are of limited therapeutic use due to the emergence of resistance mutations in the protein. Herein, using an assay that involves expression of the protein in Escherichia coli with resultant growth retardation, we present quantitative measurements of channel blocker interactions. Comparison of detailed Ks measurements of different drugs for several influenza channels, shows that the swine flu M2 exhibits the highest resistance to aminoadamantyls of any channel known to date. From the perspective of the blocker, we show that rimantadine is consistently a better blocker of M2 than amantadine. Taken together, such detailed and quantitative analyses provide insight into the mechanism of this important and pharmaceutically relevant channel blocker system.
Bibliographical noteFunding Information:
This work was supported in part by grants from the National Institutes of Health ( R21AI064797 ), the Israeli Science Foundation ( 784/01 , 1249/05 , and 1581/08 ) and the Horowitz Foundation . ITA is the Arthur Lejwa Professor of Structural Biochemistry at the Hebrew University of Jerusalem. The authors are indebted to Dr. Tsafi Danieli from the protein expression facility at the Wolfson Centre for Applied Structural Biology for numerous helpful discussions and advice.
- Channel blocker