Figure 2.

A schematic representation of the AIS motif within Na_v channels.

The Na_v channels comprise of four domains (D-I–IV), and each domain contains six transmembrane segments (TS1–TS6). The AIS motif (enlarged area) is located between the II and III domains of the Na_v channels, and is made up of different 27 amino acids, with three main ones: serine (S) at the positions 1112, 1123, 1124, and 1126; glutamate (E) at the positions 1111 and 1115; and aspartate (D) at the position, 1113. Serine is important because the phosphorylation of Na_v channels is accomplished by CK2, and CK2 is specific for serine or threonine. The presence of negative residues, such as glutamate and aspartate is also significant because they provide the support for the CK2-mediated phosphorylation of serine. Moreover, glutamate and aspartate assist CK2 in the identification of serine as a target for phosphorylation. This figure was produced using Servier Medical Art (https://smart.servier.com). AIS: Axon initial segment; AnkG: ankyrin-G; Na_v: voltage-gated sodium channel.