Depiction of the relative locations of amino acid substitutions caused by the novel allele. A schematic representation of the A transferase resulting from transcription and translation of the novel allele is shown on the left side whilst a computed 3D-model on black background is displayed on the right side. In the former, all amino acid substitutions resulting from the four missense mutations in the O1v-A2 hybrid are shown as coloured circles highlighted by dotted arrows. In the latter, only two of the mutated positions could be displayed in the model since the two N-terminal substitutions were not included in the expressed soluble portion of the crystallized A transferase  on which the template structure (molecular coordinate file 1LZ0 in the NCBI structure database) was based. The 3D surface model was created with the DeepView Swiss Pdb Viewer version 3.7, an interactive molecular graphics programme for viewing and analyzing protein structure (http://www.expasy.org/spdbv and ) using the molecular surface mode and the 3D rendering display option. No effort was made to calculate the possible structural alterations caused by the amino acid changes. The original sequence expressed for the crystallographic study  was used for the analysis. Residue positions 63 and 74 are highlighted in red and green, respectively, to show their relative locations in the model. In addition, the DXD motif (present in almost all glycosyltransferases, here as DVD capable of binding the UDP part of the nucleotide-sugar substrate) is shown in blue in order to highlight the catalytic cleft. The different regions of the glycosyltransferase are shown according to Paulson and Colley  and the transmembrane domain (amino acids 17–37) is based on the hydrophobicity plot and amino acid composition originally reported by Yamamoto et al. . The black X represents the approximate location of a proteolytic cleavage site for generation of the soluble glycosyltransferase found in body fluids.