Publications (22) View all
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Article: Structural basis for antigenic peptide precursor processing by the endoplasmic reticulum aminopeptidase ERAP1.
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ABSTRACT: ERAP1 trims antigen precursors to fit into MHC class I proteins. To fulfill this function, ERAP1 has unique substrate preferences, trimming long peptides but sparing shorter ones. To identify the structural basis for ERAP1's unusual properties, we determined the X-ray crystal structure of human ERAP1 bound to bestatin. The structure reveals an open conformation with a large interior compartment. An extended groove originating from the enzyme's catalytic center can accommodate long peptides and has features that explain ERAP1's broad specificity for antigenic peptide precursors. Structural and biochemical analyses suggest a mechanism for ERAP1's length-dependent trimming activity, whereby binding of long rather than short substrates induces a conformational change with reorientation of a key catalytic residue toward the active site. ERAP1's unique structural elements suggest how a generic aminopeptidase structure has been adapted for the specialized function of trimming antigenic precursors.Nature Structural & Molecular Biology 05/2011; 18(5):604-13. · 12.71 Impact Factor -
Article: Cutting Edge: Coding single nucleotide polymorphisms of endoplasmic reticulum aminopeptidase 1 can affect antigenic peptide generation in vitro by influencing basic enzymatic properties of the enzyme.
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ABSTRACT: ER aminopeptidase 1 (ERAP1) customizes antigenic peptide precursors for MHC class I presentation and edits the antigenic peptide repertoire. Coding single nucleotide polymorphisms (SNPs) in ERAP1 were recently linked with predisposition to autoimmune disease, suggesting a link between pathogenesis of autoimmunity and ERAP1-mediated Ag processing. To investigate this possibility, we analyzed the effect that disease-linked SNPs have on Ag processing by ERAP1 in vitro. Michaelis-Menten analysis revealed that the presence of SNPs affects the Michaelis constant and turnover number of the enzyme. Strikingly, specific ERAP1 allele-substrate combinations deviate from standard Michaelis-Menten behavior, demonstrating substrate-inhibition kinetics; to our knowledge, this phenomenon has not been described for this enzyme. Cell-based Ag-presentation analysis was consistent with changes in the substrate inhibition constant K(i), further supporting that ERAP1 allelic composition may affect Ag processing in vivo. We propose that these phenomena should be taken into account when evaluating the possible link between Ag processing and autoimmunity.The Journal of Immunology 02/2011; 186(4):1909-13. · 5.79 Impact Factor -
Article: Identification of a critical T(Q/D/E)x5ADx2(I/L) motif from primate lentivirus Vif proteins that regulate APOBEC3G and APOBEC3F neutralizing activity.
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ABSTRACT: Primate lentiviruses are unique in that they produce several accessory proteins to help in the establishment of productive viral infection. The major function of these proteins is to clear host resistance factors that inhibit viral replication. Vif is one of these proteins. It functions as an adaptor that binds to the cytidine deaminases APOBEC3G (A3G) and APOBEC3F (A3F) and bridges them to a cullin 5 (Cul5) and elongin (Elo) B/C E3 ubiquitin ligase complex for proteasomal degradation. So far, 11 discontinuous domains in Vif have been identified that regulate this degradation process. Here we report another domain, T(Q/D/E)x(5)ADx(2)(I/L), which is located at residues 96 to 107 in the human immunodeficiency virus type 1 (HIV-1) Vif protein. This domain is conserved not only in all HIV-1 subtypes but also in other primate lentiviruses, including HIV-2 and simian immunodeficiency virus (SIV), which infects rhesus macaques (SIVmac) and African green monkeys (SIVagm). Mutations of the critical residues in this motif seriously disrupted Vif's neutralizing activity toward both A3G and A3F. This motif regulates Vif interaction not only with A3G and A3F but also with Cul5. When this motif was inactivated in the HIV-1 genome, Vif failed to exclude A3G and A3F from virions, resulting in abortive HIV replication in nonpermissive human T cells. Thus, T(Q/D/E)x(5)ADx(2)(I/L) is a critical functional motif that directly supports the adaptor function of Vif and is an attractive target for inhibition of Vif function.Journal of Virology 09/2010; 84(17):8561-70. · 5.40 Impact Factor -
Article: Placental leucine aminopeptidase efficiently generates mature antigenic peptides in vitro but in patterns distinct from endoplasmic reticulum aminopeptidase 1.
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ABSTRACT: All three members of the oxytocinase subfamily of M1 aminopeptidases, endoplasmic reticulum aminopeptidase 1 (ERAP1), ERAP2, and placental leucine aminopeptidase (PLAP), also known as insulin-regulated aminopeptidase, have been implicated in the generation of MHC class I-presented peptides. ERAP1 and 2 trim peptides in the endoplasmic reticulum for direct presentation, whereas PLAP has been recently implicated in cross-presentation. The best characterized member of the family, ERAP1, has unique enzymatic properties that fit well with its role in Ag processing. ERAP1 can trim a large variety of long peptide sequences and efficiently accumulate mature antigenic epitopes of 8-9 aa long. In this study, we evaluate the ability of PLAP to process antigenic peptide precursors in vitro and compare it with ERAP1. We find that, similar to ERAP1, PLAP can trim a variety of long peptide sequences efficiently and, in most cases, accumulates appreciable amounts of correct length mature antigenic epitope. Again, similar to ERAP1, PLAP continued trimming some of the epitopes tested and accumulated smaller products effectively destroying the epitope. However, the intermediate accumulation properties of ERAP1 and PLAP are distinct and epitope dependent, suggesting that these two enzymes may impose different selective pressures on epitope generation. Overall, although PLAP has the necessary enzymatic properties to participate in generating or destroying MHC class I-presented peptides, its trimming behavior is distinct from that of ERAP1, something that supports a separate role for these two enzymes in Ag processing.The Journal of Immunology 08/2010; 185(3):1584-92. · 5.79 Impact Factor -
Article: Identification of 81LGxGxxIxW89 and 171EDRW174 domains from human immunodeficiency virus type 1 Vif that regulate APOBEC3G and APOBEC3F neutralizing activity.
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ABSTRACT: The human cytidine deaminases APOBEC3G (A3G) and APOBEC3F (A3F) potently restrict human immunodeficiency virus type 1 (HIV-1) replication, but they are neutralized by the viral protein Vif. Vif bridges A3G and A3F with a Cullin 5 (Cul5)-based E3 ubiquitin ligase and mediates their proteasomal degradation. This mechanism has been extensively studied, and several Vif domains have been identified that are critical for A3G and A3F neutralization. Here, we identified two additional domains. Via sequence analysis of more than 2,000 different HIV-1 Vif proteins, we identified two highly conserved amino acid sequences, (81)LGxGxSIEW(89) and (171)EDRWN(175). Within the (81)LGxGxSIEW(89) sequence, residues L81, G82, G84, and, to a lesser extent, I87 and W89 play very critical roles in A3G/A3F neutralization. In particular, residues L81 and G82 determine Vif binding to A3F, residue G84 determines Vif binding to both A3G and A3F, and residues (86)SIEW(89) affect Vif binding to A3F, A3G, and Cul5. Accordingly, this (81)LGxGxSIEW(89) sequence was designated the (81)LGxGxxIxW(89) domain. Within the (171)EDRWN(175) sequence, all residues except N175 are almost equally important for regulation of A3F neutralization, and consistently, they determine Vif binding only to A3F. Accordingly, this domain was designated (171)EDRW(174). The LGxGxxIxW domain is also partially conserved in simian immunodeficiency virus Vif from rhesus macaques (SIVmac239) and has a similar activity. Thus, (81)LGxGxxIxW(89) and (171)EDRW(174) are two novel functional domains that are very critical for Vif function. They could become new targets for inhibition of Vif activity during HIV replication.Journal of Virology 03/2010; 84(11):5741-50. · 5.40 Impact Factor
