A new model for the membrane topology of glucose-6-phosphatase: the enzyme involved in von Gierke disease.

Very recently we have proposed [Hemrika et al. (1997) Proc. Natl. Acad. Sci. USA 94, 2145-2149] that the active site of the vanadate-containing chloroperoxidase from the fungus Curvularia inaequalis, of which the tertiary structure is known, is structurally very similar to that of the membrane-bound mammalian glucose-6-phosphatases for which no structural data are available. The proposed active site of glucose-6-phosphatase, however, is incompatible with the six transmembrane-helix topology model that is currently used. Here we present a new topology model for glucose-6-phosphatase which is in agreement with all available data.