Sitting in—not through—a membrane

A putative acyl transferase is lodged in both inner and outer mitochondrial membranes without poking fully through either one, report Claypool et al. (page 379). Point mutations that cause mislocalization of this tafazzin protein within mitochondria or alter its macromolecular interactions are sufficient to cause Barth syndrome.

Barth syndrome is a human disorder in which mitochondrial dysfunction, including disturbed lipid composition, leads to cardiac myopathy and other problems. Previous work showed that the yeast tafazzin protein (Taz1p) is a suitable model for the syndrome and that Taz1p localizes to mitochondria.

In the current work, the authors found that Taz1p localized to the inner and outer membranes of the mitochondria, but only to the leaflets that face the intermembrane space. A central loop in the Taz1p protein inserted into the membranes and hung onto them as...