Figure 1.

(a) GtgE^43–214 was subjected to limited proteolysis by subtilisin protease (Sigma–Aldrich) as described. Edman sequencing indicated that the two main cleavage products were N-terminally truncated to residue 79. C-­terminal residue limits were estimated based on the molecular weight of the cleavage products as observed by SDS–PAGE. The crystallized construct is shown in red. Molecular-mass markers (left lane) are labelled in kDa. (b) Native and selenomethionine-derivative crystals of GtgE^79–214 grown in 0.2 M Li₂SO₄, 1.75 M ammonium sulfate, 0.1 M Tris pH 7.0 at 4°C. (c) 2F _o − F _c model-phased electron-density map contoured at 2σ shown in blue with the final refined model shown.