SEDL (known also as sedlin) is a 140 amino-acid protein with a putative role in endoplasmic reticulum-to-Golgi transport. Several missense mutations and deletion mutations in the SEDL gene, which result in protein truncation by frame shift, are responsible for spondyloepiphyseal dysplasia tarda, a progressive skeletal disorder. The protein is identical to MIP-2A, which was shown to interact physically with c-myc promotor-binding protein 1 (MBP-1) and relieve the regulatory role of MBP-1 as a general transcription repressor. In order to gain insights into the function of SEDL by structural analysis, the protein was overexpressed and crystallized as a first step. SEDL was overexpressed in Escherichia coli and crystallized using the hanging-drop vapour-diffusion method at 298 K. The crystals belong to the orthorhombic space group C222(1), with unit-cell parameters a = 46.69, b = 101.30, c = 66.15 A. The unit cell is likely to contain one molecule of SEDL, with a crystal volume per protein mass (V(M)) of 2.36 A(3)Da(-1) and a solvent content of about 47.9% by volume. A native data set to 2.8 A resolution was obtained from a flash-cooled crystal using synchrotron radiation.