Characterization of Escherichia coli OtsA, a trehalose-6-phosphate synthase from glycosyltransferase family 20

The Ots gene cluster of Escherichia coli encodes the synthetic apparatus for the formation of α,α‐1,1‐trehalose, a non‐reducing glucose disaccharide. The otsA gene encodes a trehalose‐6‐phosphate synthase, a glycosyltransferase which catalyses the synthesis of α,α‐­1,1‐trehalose‐6‐phosphate from glucose‐6‐phosphate using a UDP‐glucose donor. It has been classified into glycosyltransferase family GT‐20 based upon amino‐acid sequence similarities. The otsA gene has been cloned and recombinant protein overexpressed using a pET‐based system in E. coli BL21 cells. The recombinant protein (MW ≃ 54.7 kDa) is active and has been crystallized in two forms suitable for X‐ray diffraction analysis. The first is orthorhombic, P212121, with unit‐cell parameters a = 104.1, b = 127.8, c = 179.9 Å. Data for this form have been collected to 3.0 Å resolution at the CLRC Daresbury Synchrotron Radiation Source. The second form has unit‐cell parameters a = b = 141.9, c = 317.8 Å and displays the apparent space group P42. These crystals diffract beyond 2 Å resolution, but display merohedral twinning.