The structure of a fragment of human CD4 containing two immunoglobulin (Ig)-like domains has been determined by X-ray crystallography and refined at 2.2 A resolution. The structure determination involved iterative building and simulated-annealing refinement, beginning with a partial model ...
The structure of a fragment of human CD4 containing two immunoglobulin (Ig)-like domains has been determined by X-ray crystallography and refined at 2.2 A resolution. The structure determination involved iterative building and simulated-annealing refinement, beginning with a partial model. Comparison of domain 1 with an Ig variable domain shows that CD4 has a long and prominent CDR2-like loop (the C"C" corner) and shortened CC' and FG loops (which mediate dimerization in IgV modules). Comparison of domain 2 with Ig modules and domain 1 shows that it can be described as a truncated Ig V domain, in which strands C" and D are deleted. The intersheet disulfide in domain 2 is absent, and there is an altered packing of the two beta-sheets together with a remodeling of the hydrophobic core. The interface between domains 1 and 2 is a lap joint with an extensive hydrophobic surface. The key features of domain 1 that contribute to the interface are found at corresponding positions in domain 2, leading us to propose that the contact between domains 2 and 3 will resemble the one between domains 1 and 2.
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Atomic Structure of a Fragment of Human Cd4 Containing Two Immunoglobulin-Like Domains Wang, J., Yan, Y., Garrett, T.P.J., Liu, J., Rodgers, D., Garlick, R.L., Tarr, G.E., Husain, Y., Reinherz, E.L., Harrison, S.C. (1990) Nature 348: 411
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