Voltage-gated proton channels in polyneopteran insects.

Voltage-gated proton channels (HV 1) are expressed in eukaryotes, including basal hexapods and polyneopteran insects. However, currently there is little known about HV 1 channels in insects. A characteristic aspartate that functions as the proton selectivity filter (SF) and the RxWRxxR voltage-sensor motif are conserved structural elements in HV 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 Glu at SF was found in Phasmatodea and Mantophasmatodea. Additionally, we analysed the expression and function of HV 1 in the phasmatodean stick insect Extatosoma tiaratum (Et). EtHV 1 is strongly expressed in nervous tissue and shows pronounced inward proton conduction. This is the first study of a natural occurring glutamate within the SF of a functional HV 1 and might be instrumental in uncovering the physiological function of HV 1 in insects.