1jl4
From Proteopedia
CRYSTAL STRUCTURE OF THE HUMAN CD4 N-TERMINAL TWO DOMAIN FRAGMENT COMPLEXED TO A CLASS II MHC MOLECULE
Structural highlights
Function[CD4_HUMAN] Accessory protein for MHC class-II antigen/T-cell receptor interaction. May regulate T-cell activation. Induces the aggregation of lipid rafts. [TRFE_CHICK] Transferrins are iron binding transport proteins which can bind two Fe(3+) ions in association with the binding of an anion, usually bicarbonate. Responsible for the transport of iron from sites of absorption and heme degradation to those of storage and utilization. There are two forms of hen transferrin, ovotransferrin, found in the ovoducts and, serum transferrin, secreted by the liver. Serum transferrin may also have a role in stimulating cell proliferation and is regulated by iron levels. Ovotransferrin has a bacteriostatic function and, is not controlled by iron levels. Evolutionary Conservation Check, as determined by ConSurfDB. You may read the explanation of the method and the full data available from ConSurf. Publication Abstract from PubMedThe structural basis of the interaction between the CD4 coreceptor and a class II major histocompatibility complex (MHC) is described. The crystal structure of a complex containing the human CD4 N-terminal two-domain fragment and the murine I-A(k) class II MHC molecule with associated peptide (pMHCII) shows that only the "top corner" of the CD4 molecule directly contacts pMHCII. The CD4 Phe-43 side chain extends into a hydrophobic concavity formed by MHC residues from both alpha 2 and beta 2 domains. A ternary model of the CD4-pMHCII-T-cell receptor (TCR) reveals that the complex appears V-shaped with the membrane-proximal pMHCII at the apex. This configuration excludes a direct TCR-CD4 interaction and suggests how TCR and CD4 signaling is coordinated around the antigenic pMHCII complex. Human CD4 binds to HIV gp120 in a manner strikingly similar to the way in which CD4 interacts with pMHCII. Additional contacts between gp120 and CD4 give the CD4-gp120 complex a greater affinity. Thus, ligation of the viral envelope glycoprotein to CD4 occludes the pMHCII-binding site on CD4, contributing to immunodeficiency. Crystal structure of the human CD4 N-terminal two-domain fragment complexed to a class II MHC molecule.,Wang JH, Meijers R, Xiong Y, Liu JH, Sakihama T, Zhang R, Joachimiak A, Reinherz EL Proc Natl Acad Sci U S A. 2001 Sep 11;98(19):10799-804. Epub 2001 Sep 4. PMID:11535811[1] From MEDLINE®/PubMed®, a database of the U.S. National Library of Medicine. See AlsoReferences
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