Voltage-gated proton channels in polyneopteran insects

Voltage-gated proton channels (H_V 1) are expressed in eukaryotes, including basal hexapods and polyneopteran insects. However, currently, there is little known about H_V 1 channels in insects. A characteristic aspartate (Asp) that functions as the proton selectivity filter (SF) and the RxWRxxR voltage-sensor motif are conserved structural elements in H_V 1 channels. By analysing Transcriptome Shotgun Assembly (TSA) databases, we found 33 polyneopteran species meeting these structural requirements. Unexpectedly, an unusual natural variation Asp to glutamate (Glu) at SF was found in Phasmatodea and Mantophasmatodea. Additionally, we analysed the expression and function of H_V 1 in the phasmatodean stick insect Extatosoma tiaratum (Et). EtH_V 1 is strongly expressed in nervous tissue and shows pronounced inward proton conduction. This is the first study of a natural occurring Glu within the SF of a functional H_V 1 and might be instrumental in uncovering the physiological function of H_V 1 in insects.