ATP2B3 and infection: OpcA, which is involved in adhesion to epithelial and endothelial cells important in the infection process32,33, has been shown to be phase variable and regulated by homopolymeric cytidine residues in the promoter sequence; ≤ 10 or ≥ 15 cytidine residues suppress expression, 12–13 cytidine residues lead to efficient expression, and 11 or 14 lead to intermediate expression34.