Crystallization and preliminary X-ray analysis of crustacean hyperglycaemic hormone from the kuruma prawn Marsupenaeus japonicus in its weakly active precursor form

Crustacean hyperglycaemic hormone (CHH) plays a pivotal role in the regulation of glucose metabolism in crustaceans. Pej-SGP-I, one of the six known CHHs in the kuruma prawn Marsupenaeus japonicus, was heterolo-gously expressed in Escherichia coli as an N-terminally His-tagged and Nus-tagged protein in its weakly active precursor form, Pej-SGP-I-Gly, which has an extra glycine residue at the C-terminus. The recombinant peptide was subjected to affinity purification, tag removal, further purification and crystallization by the sitting-drop vapour-diffusion method using NaCl as the main precipitant. The crystals diffracted to 1.95 Å resolution and the space group was assigned as primitive orthorhombic P2 ₁2 ₁2 ₁, with unit-cell parameters a = 40.19, b = 53.65, c = 53.63 Å. The Matthews coefficient (V M = 1.73 Å ³ Da ^-1) indicated that the crystal contained two Pej-SGP-I-Gly molecules per asymmetric unit, with a solvent content of 29.0%.