1r5i: Difference between revisions

[[Image:1r5i.gif|left|200px]]<br /><applet load="1r5i" size="350" color="white" frame="true" align="right" spinBox="true"  

Mycoplasma arthritidis-derived mitogen (MAM) is a superantigen that can activate large fractions of T cells bearing particular TCR Vbeta elements. Here we report the crystal structure of MAM complexed with a major histocompatibility complex (MHC) antigen, HLA-DR1, loaded with haemagglutinin peptide 306-318 (HA). The structure reveals that MAM has a novel fold composed of two alpha-helical domains. This fold is entirely different from that of the pyrogenic superantigens, consisting of a beta-grasped motif and a beta barrel. In the complex, the N-terminal domain of MAM binds orthogonally to the MHC alpha1 domain and the bound HA peptide, and to a lesser extent to the MHC beta1 domain. Two MAM molecules form an asymmetric dimer and cross-link two MHC antigens to form a plausible, dimerized MAM-MHC complex. These data provide the first crystallographic evidence that superantigens can dimerize MHC molecules. Based on our structure, a model of the TCR2MAM2MHC2 complex is proposed.

1R5I is a [http://en.wikipedia.org/wiki/Protein_complex Protein complex] structure of sequences from [http://en.wikipedia.org/wiki/Homo_sapiens Homo sapiens] and [http://en.wikipedia.org/wiki/Mycoplasma_arthritidis Mycoplasma arthritidis] with <scene name='pdbligand=PO4:'>PO4</scene> as [http://en.wikipedia.org/wiki/ligand ligand]. Full crystallographic information is available from [http://oca.weizmann.ac.il/oca-bin/ocashort?id=1R5I OCA].  

[[Category: Drozd, S J.]]

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