Figure 3:

Sucrase–isomaltase is located at the brush-border membrane of the small intestine. Enzymatic domains are in the gut lumen, connected to the cellular membrane by a short linker sequence. The c.273_274delAG mutation (red circle) results in disruption of the usual reading frame (p.Gly92Leufs*8), completely abolishing both enzymatic activities (depicted in grey). Owing to nonsense-mediated decay, there is a high likelihood that the resulting messenger RNA product is targeted for degradation (i.e., is not translated and is functionally null).