Interestingly, heteromerization with Kir5.1 also shifts intracellular pH dependence of both Kir4.1 and Kir4.2 (which does not heteromerize with Kir4.1, but may compete with Kir4.1 for Kir5.1) into a more physiologically relevant pH range (Tucker et al., 2000; Pessia et al., 2001), and Kir4.1/Kir5.1 heteromeric channels may be involved in the pH-dependent regulation of respiration (Trapp et al., 2011): see section “Kir5.1 Variants: A Risk Factor for SIDS?”. This evidence concerns the gene KCNJ16 and sudden infant death syndrome.