Identification of an H V 1 voltage‐gated proton channel in insects

The voltage‐gated proton channel 1 ( H V 1) is an important component of the cellular proton extrusion machinery and is essential for charge compensation during the respiratory burst of phagocytes. H V 1 has been identified in a wide range of eukaryotes throughout the animal kingdom, with the exception of insects. Therefore, it has been proposed that insects do not possess an H V 1 channel. In the present study, we report the existence of an H V 1‐type proton channel in insects. We searched insect transcriptome shotgun assembly ( TSA ) sequence databases and found putative H V 1 orthologues in various polyneopteran insects. To confirm that these putative H V 1 orthologues were functional channels, we studied the H V 1 channel of Nicoletia phytophila (Np H V 1), an insect of the Zygentoma order, in more detail. Np H V 1 comprises 239 amino acids and is 33% identical to the human voltage‐gated proton channel 1. Patch clamp measurements in a heterologous expression system showed proton selectivity, as well as pH ‐ and voltage‐dependent gating. Interestingly, Np H V 1 shows slightly enhanced pH ‐dependent gating compared to the human channel. Mutations in the first transmembrane segment at position 66 (Asp66), the presumed selectivity filter, lead to a loss of proton‐selective conduction, confirming the importance of this aspartate residue in voltage‐gated proton channels. Database Nucleotide sequence data have been deposited in the GenBank database under accession number KT780722 .