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.