Atomistic structure and dynamics of the human MHC-I peptide-loading complex

Fisette, Olivier; Schröder, Gunnar F.; Schäfer, Lars V.

doi:10.1073/pnas.2004445117

Cited by 45 publications

(41 citation statements)

References 63 publications

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“…To evaluate the stability of our MD simulations, we examined Cα root-mean-square deviation (RMSD) as a function of simulation time for the entire HLA-A*02:01/TAPBPR complex, as well as for the individual components of the system, relative to a global reference frame defined by the starting structure. The HLA-A*02:01/TAPBPR complex and its components exhibited Cα RMSD values that are in a similar range to those observed by other groups performing MD simulations on analogous systems 24,25 (Supplementary Fig. 1d).…”

Section: Unexpected Conformational Plasticity Of the Tapbpr G24-r36 Loopsupporting

confidence: 79%

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TAPBPR promotes antigen loading on MHC-I molecules using a peptide trap

et al. 2021

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Chaperones Tapasin and TAP-binding protein related (TAPBPR) perform the important functions of stabilizing nascent MHC-I molecules (chaperoning) and selecting high-affinity peptides in the MHC-I groove (editing). While X-ray and cryo-EM snapshots of MHC-I in complex with TAPBPR and Tapasin, respectively, have provided important insights into the peptide-deficient MHC-I groove structure, the molecular mechanism through which these chaperones influence the selection of specific amino acid sequences remains incompletely characterized. Based on structural and functional data, a loop sequence of variable lengths has been proposed to stabilize empty MHC-I molecules through direct interactions with the floor of the groove. Using deep mutagenesis on two complementary expression systems, we find that important residues for the Tapasin/TAPBPR chaperoning activity are located on a large scaffolding surface, excluding the loop. Conversely, loop mutations influence TAPBPR interactions with properly conformed MHC-I molecules, relevant for peptide editing. Detailed biophysical characterization by solution NMR, ITC and FP-based assays shows that the loop hovers above the MHC-I groove to promote the capture of incoming peptides. Our results suggest that the longer loop of TAPBPR lowers the affinity requirements for peptide selection to facilitate peptide loading under conditions and subcellular compartments of reduced ligand concentration, and to prevent disassembly of high-affinity peptide-MHC-I complexes that are transiently interrogated by TAPBPR during editing.

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Section: Unexpected Conformational Plasticity Of the Tapbpr G24-r36 Loopsupporting

confidence: 79%

“…1a-e). The mobility of the tapasin loop has been investigated by recent μstimescale MD simulations of the native peptide loading complex, which provided evidence that the Asn86-glycan moiety promotes movement of the shorter tapasin loop toward the MHC-I groove 25 . How MHC-I glycosylation at the conserved Asn86 Fig.…”

Section: Discussionmentioning

confidence: 99%

TAPBPR promotes antigen loading on MHC-I molecules using a peptide trap

et al. 2021

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“…As presented in Figure 5c, the N-terminal region of the mAb 16 epitope was located in an α-helix structure. Although the complete epitope could not be determined from the crystal structure, recent findings have proposed that the missing region of the epitope is found in an α-helix structure as well [17,46,47]. Collectively, these findings contribute to increased knowledge of the crystal structure of the C-terminal end of CRT, as only the first 365 aas of CRT have been crystallized.…”

Section: Discussionmentioning

confidence: 99%

Epitope Mapping of Monoclonal Antibodies to Calreticulin Reveals That Charged Amino Acids Are Essential for Antibody Binding

et al. 2021

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Calreticulin is a chaperone protein, which is associated with myeloproliferative diseases. In this study, we used resin-bound peptides to characterize two monoclonal antibodies (mAbs) directed to calreticulin, mAb FMC 75 and mAb 16, which both have significantly contributed to understanding the biological function of calreticulin. The antigenicity of the resin-bound peptides was determined by modified enzyme-linked immunosorbent assay. Specific binding was determined to an 8-mer epitope located in the N-terminal (amino acids 34–41) and to a 12-mer peptide located in the C-terminal (amino acids 362–373). Using truncated peptides, the epitopes were identified as TSRWIESK and DEEQRLKEEED for mAb FMC 75 and mAb 16, respectively, where, especially the charged amino acids, were found to have a central role for a stable binding. Further studies indicated that the epitope of mAb FMC 75 is assessable in the oligomeric structure of calreticulin, making this epitope a potential therapeutic target.

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“…We note that while this is also the case for the X-ray crystallography and other biophysical studies in our field (Jiang et al, 2017;McShan et al, 2018;Morozov et al, 2016;Thomas and Tampé, 2017), there may be differences in MHC-I / chaperone interactions for proteins expressed in mammalian cells, primarily due to glycosylation (Neerincx and Boyle, 2019). For example, MD simulations of the peptide loading complex suggest that the MHC-I-linked glycan promotes movement of the tapasin loop toward the peptide binding groove of the MHC-I (Fisette et al, 2020). Secondly, due to the lack of an experimental HLA-A*02:01/TAPBPR structure, our study is restricted to interpreting models built from available X-ray structures as templates (Fig.…”

Section: Discussionmentioning

confidence: 64%

TAPBPR Promotes Antigen Loading on MHC-I Molecules Using a Peptide Trap

McShan

Devlin

Morozov

et al. 2020

Preprint

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Chaperones Tapasin and TAP-binding protein related (TAPBPR) perform the important functions of stabilizing nascent MHC-I molecules (chaperoning) and selecting high affinity peptides in the MHC-I groove (editing). While X-ray and cryo-EM snapshots of MHC-I in complex with TAPBPR and Tapasin, respectively, have provided important insights into the peptide-deficient MHC-I groove structure, the molecular mechanism through which these chaperones influence the selection of specific amino acid sequences remains incompletely characterized. Based on structural and functional data, a loop sequence of variable lengths has been proposed to stabilize empty MHC-I molecules through direct interactions with the floor of the groove. Using deep mutagenesis on two complementary expression systems, we find that important residues for the Tapasin/TAPBPR chaperoning activity are located on a large scaffolding surface, excluding the loop. Conversely, loop mutations influence TAPBPR interactions with properly conformed MHC-I molecules, relevant for peptide editing. Detailed biophysical characterization by solution NMR, ITC and FP-based shows that the loop hovers above the MHC-I groove to promote the capture of incoming peptides, thereby acting as a trap. Our results suggest that the longer loop of TAPBPR lowers the affinity requirements for peptide selection to facilitate peptide loading under conditions and subcellular compartments of reduced ligand concentration, and to prevent disassembly of high affinity peptide-MHC-I complexes that are transiently interrogated by TAPBPR during editing.

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Atomistic structure and dynamics of the human MHC-I peptide-loading complex

Cited by 45 publications

References 63 publications

TAPBPR promotes antigen loading on MHC-I molecules using a peptide trap

TAPBPR promotes antigen loading on MHC-I molecules using a peptide trap

Epitope Mapping of Monoclonal Antibodies to Calreticulin Reveals That Charged Amino Acids Are Essential for Antibody Binding

TAPBPR Promotes Antigen Loading on MHC-I Molecules Using a Peptide Trap

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