Figure 4.

Metabolism of E2 to E1 in HEK-293 cells expressing human 17βHSD2 or E116 mutations. A, Alignment of short-chain dehydrogenases identifies residue E116 is the charged residue corresponding to R38 of 17βHSD1. B, E1 (0.1 μm) conversion to E2 by cells expressing wild-type (circles) or mutations E116D (squares), E116G (triangles), and E116R (inverted triangles), E116G+N117R (diamonds), and chimera N-11βHSD2-C-17βHSD2-E116G (stars) in complete medium is shown as a function of time. Data points are means ± sd of two to five experiments, and curves are best fits of the data to the function: ƒ(t) = A(1 − e^−kt). Equilibrium steroid distributions, derived by setting t = ∞, are summarized in Table 1 (r² > 0.99 for all curves).