From Proteopediaproteopedia link
Crystal structure of HLA-B*4402 in complex with the R5A/F7A double mutant of a self-peptide derived from DPA*0201
[B2MG_HUMAN] Defects in B2M are the cause of hypercatabolic hypoproteinemia (HYCATHYP) [MIM:241600]. Affected individuals show marked reduction in serum concentrations of immunoglobulin and albumin, probably due to rapid degradation. Note=Beta-2-microglobulin may adopt the fibrillar configuration of amyloid in certain pathologic states. The capacity to assemble into amyloid fibrils is concentration dependent. Persistently high beta(2)-microglobulin serum levels lead to amyloidosis in patients on long-term hemodialysis.            
[1B44_HUMAN] Involved in the presentation of foreign antigens to the immune system. [B2MG_HUMAN] Component of the class I major histocompatibility complex (MHC). Involved in the presentation of peptide antigens to the immune system.
Publication Abstract from PubMed
Residues within processed protein fragments bound to major histocompatibility complex class I (MHC-I) glycoproteins have been considered to function as a series of "independent pegs" that either anchor the peptide (p) to the MHC-I and/or interact with the spectrum of alphabeta-T-cell receptors (TCRs) specific for the pMHC-I epitope in question. Mining of the extensive pMHC-I structural database established that many self- and viral peptides show extensive and direct interresidue interactions, an unexpected finding that has led us to the idea of "constrained" peptides. Mutational analysis of two constrained peptides (the HLA B44 restricted self-peptide (B44DPalpha-EEFGRAFSF) and an H2-D(b) restricted influenza peptide (D(b)PA, SSLENFRAYV) demonstrated that the conformation of the prominently exposed arginine in both peptides was governed by interactions with MHC-I-orientated flanking residues from the peptide itself. Using reverse genetics in a murine influenza model, we revealed that mutation of an MHC-I-orientated residue (SSLENFRAYV --> SSLENARAYV) within the constrained PA peptide resulted in a diminished cytotoxic T lymphocyte (CTL) response and the recruitment of a limited pMHC-I specific TCR repertoire. Interactions between individual peptide positions can thus impose fine control on the conformation of pMHC-I epitopes, whereas the perturbation of such constraints can lead to a previously unappreciated mechanism of viral escape.
Constraints within major histocompatibility complex class I restricted peptides: presentation and consequences for T-cell recognition.,Theodossis A, Guillonneau C, Welland A, Ely LK, Clements CS, Williamson NA, Webb AI, Wilce JA, Mulder RJ, Dunstone MA, Doherty PC, McCluskey J, Purcell AW, Turner SJ, Rossjohn J Proc Natl Acad Sci U S A. 2010 Mar 23;107(12):5534-9. Epub 2010 Mar 8. PMID:20212169
From MEDLINE®/PubMed®, a database of the U.S. National Library of Medicine.