Fig 1. Overview of CD23 constructs.

A, Amino acid sequence of CD23. Indicated are the constructs CD23A, CD23B, CD23C, and CD23D; peptides (P1-P7) used to raise specific antisera (brown bars); N-linked glycosylation sites (red letters); and secondary structure and surface exposure (blue bars) of amino acids, as derived from the crystal structure PDB:2H2T (Wurzburg et al¹²). A region in which no data are available (R253-E257) is indicated by a gray bar. Amino acids involved in IgE binding according to Hibbert et al¹³ and Dhaliwal et al¹⁵ are shown in green and blue, respectively. Residues involved in IgE binding according to both publications are shown in orange. Cysteine residues involved in disulfide bond formation are numbered. CD23 domains are shaded (intracellular domain: red; transmembrane domain: yellow; stalk domain: green; head domain: purple). B, Schematic representation of the known (Wurzburg et al¹²) and predicted 3-dimensional structure of CD23. CD23 peptides are indicated. Data for region R253-E257, as well as for the C-terminal end, are not available. C, Sketch of the recombinant CD23 constructs (CD23A, CD23B, CD23C, and CD23D), as cloned into plasmid pTM1 with a C-terminal hexa-histidine tag (6xHis) and an N-terminal melittin signal sequence. Amino acids at the N- and C-terminal ends of CD23 and one mutated in CD23B are indicated in black.