Biomedical Engineering Reference
In-Depth Information
Figure 9.1
Three-dimensional structure of IL-2. Structural details courtesy of the Protein Data Bank, http://
www.rcsb.org/pdb/
residue no. 3. The mature molecule displays a molecular mass ranging from 15 to 20 kDa,
depending upon the extent of glycosylation. The carbohydrate moiety is not required for
biological activity.
X-ray diffraction analysis shows the protein to be a globular structure, consisting of four
-heli-
cal stretches interrupted by bends and loops. It appears devoid of any β-conformation and contains
a single stabilizing disulfi de linkage involving cysteine numbers 58 and 105 (Figure 9.1).
IL-2 induces its characteristic biological activities by binding a specifi c receptor on the surface
of sensitive cells. The high-affi nity receptor complex consists of three membrane-spanning
polypeptide chains (α, β and γ; Table 9.2).
α
Table 9.2
Summary of the polypeptide constituents of the high-affi nity
human IL-2 receptor
Receptor polypeptide constituent
Additional names
Molecular mass (kDa)
α
P55
Tac
55
CD25
β
P75
CD122
75
γ
P64
64
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