Structure-based modeling of the ligand binding domain of the human cell surface receptor CD23 and comparison of two independently derived molecular models.
CD23, a type II membrane receptor protein, recognizes four different ligands via its extracellular C-type lectin domain: immunoglobulin E (IgE), CD21, and the beta 2-integrins CD11b and CD11c. CD23 specifically interacts in a calcium-dependent manner, "lectin-like" with carbohydrate moieties expressed on CD21 and CD11b/c, but also "lectin-unlike" with protein epitopes on IgE. As a first step in analyzing the multiple binding specificities associated with CD23 in more detail, we report a detailed molecular model of the lectin-like domain of human CD23 (hCD23). The model was built based on information provided by X-ray structures of mannose binding protein (MBP) and E-selectin, both of which are members of the calcium-dependent (C-type) lectin superfamily. Sequence-structure comparisons suggest that hCD23 is structurally more similar to MBP than to E-selectin. The hCD23 model is compared to an independently derived model. Although the CD23-carbohydrate and CD23-protein interactions are both calcium dependent, analysis of the model suggests the presence of distinct binding sites for these ligands.
Bajorath
J
J
Bristol-Myers Squibb Pharmaceutical Research Institute, Seattle, Washington 98121, USA.
Aruffo
A
A
D000595:Amino Acid Sequence; D001665:Binding Sites; D002118:Calcium / Q000378:metabolism; D018360:Crystallography, X-Ray; D019040:E-Selectin / Q000737:chemistry; D006801:Humans; D007073:Immunoglobulin E / Q000378:metabolism; D016167:Integrin alphaXbeta2 / Q000378:metabolism; D008024:Ligands; D016177:Macrophage-1 Antigen / Q000378:metabolism; D008958:Models, Molecular; D008969:Molecular Sequence Data; D004676:Myelin Basic Protein / Q000737:chemistry; D011485:Protein Binding; D011487:Protein Conformation; D017464:Receptors, Complement 3d / Q000378:metabolism; D017455:Receptors, IgE / Q000737:chemistry* / Q000378:metabolism; D013329:Structure-Activity Relationship
D019040:E-Selectin; D016167:Integrin alphaXbeta2; D008024:Ligands; D016177:Macrophage-1 Antigen; D004676:Myelin Basic Protein; D017464:Receptors, Complement 3d; D017455:Receptors, IgE; D007073:Immunoglobulin E; D002118:Calcium