2fwo
From Proteopedia
MHC Class I H-2Kd heavy chain in complex with beta-2microglobulin and peptide derived from influenza nucleoprotein
Structural highlights
Function[HA1D_MOUSE] Involved in the presentation of foreign antigens to the immune system. [Q701N7_9INFA] Encapsidates the negative strand viral RNA, protecting it from nucleases. The encapsidated genomic RNA is termed the ribonucleoprotein (RNP) and serves as template for transcription and replication. The RNP needs to be localized in the nucleus to start an infectious cycle, but is too large to diffuse through the nuclear pore complex. NP comprises at least 2 nuclear localization signals and is responsible of the active RNP import into the nucleus through the cellular importin alpha/beta pathway. Later in the infection, nucleus export of RNP are mediated through viral proteins NEP interacting with M1 which binds nucleoproteins. It is possible that the nucleoprotein binds directly exportin-1 (XPO1) and plays an active role in RNP nuclear export. M1 interaction with RNP seems to hide nucleoprotein's nuclear localization signals. Soon after a virion infects a new cell, M1 dissociates from the RNP under acidification of the virion driven by M2 protein. Dissociation of M1 from RNP unmask nucleoprotein's nuclear localization signals, targeting the RNP to the nucleus (By similarity).[SAAS:SAAS00208116] [B2MG_MOUSE] Component of the class I major histocompatibility complex (MHC). Involved in the presentation of peptide antigens to the immune system. 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 PubMedClassic major histocompatibility complex (MHC) proteins associate with antigen- and self-derived peptides in an allele-specific manner. Herein we present the crystal structure of the MHC class I protein H-2K(d) (K(d)) expressed by BALB/c mice in complex with an antigenic peptide derived from influenza A/PR/8/34 nucleoprotein (Flu, residues 147-155, TYQRTRALV). Analysis of our structure in conjunction with the sequences of naturally processed epitopes provides a comprehensive understanding of the dominant K(d) peptide-binding motif. We find that Flu residues Tyr(P2), Thr(P5), and Val(P9) are sequestered into the B, C, and F pockets of the K(d) groove, respectively. The shape and chemistry of the polymorphic B pocket make it an optimal binding site for the side chain of Tyr(P2) as the dominant anchoring residue of nonameric peptides. The non-polar F pocket limits the amino acid repertoire at P9 to hydrophobic residues such as Ile, Leu, or Val, whereas the C pocket restricts the size of the P5-anchoring side chain. We also show that Flu is accommodated in the complex through an unfavorable kink in the otherwise extended peptide backbone due to the presence of a prominent ridge in the K(d) groove. Surprisingly, this backbone conformation is strikingly similar to D(b)-presented peptides despite the fact that these proteins employ distinct motif-anchoring strategies. The results presented in this study provide a solid foundation for the understanding of K(d)-restricted antigen presentation and recognition events. Structural definition of the H-2Kd peptide-binding motif.,Mitaksov V, Fremont DH J Biol Chem. 2006 Apr 14;281(15):10618-25. Epub 2006 Feb 10. PMID:16473882[1] From MEDLINE®/PubMed®, a database of the U.S. National Library of Medicine. References
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