M2(H37A) corresponds to the ion channel protein encoded by the Influenza A virus M2 gene (UniProtKB:P0C2M3), modified to contain a H37A amino acid substitution. The mutated ion channel acts a non-selective channel for monovalent cations, and has reduced pH sensitivity such that is constitutively active at physiological pH. These properties mean it can be used as a cell ablation tool (PMID:11918692).