Comparing among all strains, the sequence variation is largest in the linker region, including large deleted segments. Nevertheless, this region harbours a cysteine (Figure 2 ) that can be aligned over multiple NA subtypes and is conserved in N1-N5 and N8, but not in N6, N7 and N9. Earlier reports assume that, at least in related viruses, cysteines in the non-globular region could be involved in intermolecular disulfide bridges [13] [14] [15] . Alternatively, by analogy to other influenza proteins such as hemagglutinin [16] and M2 protein [17] , it cannot yet be excluded that cysteine C49 is palmitoylated and that the anchor localizes the protein to lipid rafts [18] .