A. Calnexin dissociates, thereafter class I molecule associates with the chaperone calreticulin and with tapasin
B. Peptides are transported to RER (Rough Endoplasmic Reticulum) via TAP (Transport Associated Protein)
C. Endogenous antigen is degraded by proteasome in cytosol
D. Class I MHC $\alpha$ chain binds calnexin, then $\beta$2 macroglobulin
E. MHC captures peptide and chaperones dissociate
Choose the correct answer from the options given below:
Cytosolic Pathway: Class I MHC Antigen Presentation Steps
The cytosolic pathway is crucial for presenting endogenous antigens via MHC Class I molecules to CD8+ T cells. The sequence involves antigen degradation, peptide transport, MHC molecule assembly, and peptide loading within the cell.
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C: Antigen Degradation:
Endogenous antigens (e.g., viral proteins, abnormal self-proteins) produced within the cell are first processed and degraded into small peptides by the proteasome located in the cytosol.
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B: Peptide Transport:
These generated peptides are then translocated from the cytosol into the lumen of the Rough Endoplasmic Reticulum (RER) by a specific transporter complex called TAP (Transporter Associated with Protein processing).
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D: MHC Class I Assembly Initiation:
Simultaneously, within the RER, the MHC Class I $\alpha$ chain is synthesized. It initially associates with chaperone proteins like Calnexin to ensure proper folding. Following this, $\beta$2-microglobulin ($\beta$2m) binds to the $\alpha$-chain, forming the basic MHC Class I structure.
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A: Chaperone Exchange:
Once $\beta$2m binds, Calnexin dissociates. The MHC Class I complex then interacts with a specific peptide-loading complex in the RER, which includes chaperones such as Calreticulin and Tapasin. This complex helps stabilize the MHC molecule and positions it optimally for peptide binding.
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E: Peptide Loading and Chaperone Dissociation:
The MHC Class I molecule, stabilized by the Tapasin complex, captures a high-affinity peptide delivered by TAP. Following successful peptide binding, the MHC-peptide complex undergoes a conformational change, causing the chaperones (including Tapasin) to dissociate. This stabilized complex is now ready for transport out of the RER.
This sequence ensures that endogenous antigens are effectively processed and presented on the cell surface by MHC Class I molecules.
Similar Questions
- Given below are two statements: one is labelled as Assertion (A) and the other is labelled as Reason (R).
Assertion (A): The transcripts of RNA polymerases I and III are not processed.
Reason (R): RNA polymerases I and III lack a C-terminal domain (CTD).
In the light of the above statements, choose the most appropriate answer from the options given below: - Given below are two statements: one is labelled as Assertion (A) and the other is labelled as Reason (R).
Assertion (A): Isoelectric focusing (IEF) is a highly sensitive analytical technique and is particularly useful for studying micro-heterogeneity in a protein.
Reason (R): A protein may show a single band on SDS gel, but may show three bands on an IEF gel. The method is particularly useful for separating isoenzymes, which are same forms of the different enzyme.
In the light of the above statements, choose the most appropriate answer from the options given below: - Given below are two statements: one is labelled as Assertion (A) and the other is labelled as Reason (R).
Assertion (A): It is well known that lack of insulin or thyroid hormone increases the blood cholesterol concentration, whereas excess thyroid hormone decreases the concentration.
Reason (R): These effects are probably caused by changes in the degree of activation of specific enzymes responsible for the metabolism of lipid substances.
In the light of the above statements, choose the most appropriate answer from the options given below: - Given below are two statements: one is labelled as Assertion (A) and the other is labelled as Reason (R).
Assertion (A): The molecular evidences suggest that the sister group of sponges is not choanoflagellates, but mesomycetozoa, a group of parasitic protists. So, can this hypothesis be correct given that these parasites lack collar cells?
Reason (R): The collar cells of sponges bear a significant resemblance to a choanoflagellate cell suggesting that the last common ancestor of animals and their protist sister group might have resembled a choanoflagellate. In this regard, mesomycetozoans could still be sister group of animals. The lack of collar cells in mesomycetozoans would indicate that over the time, their structure evolved in a way that it no longer resembled a choanoflagellate cell pointing out to convergent evolution.
In the light of the above statements, choose the most appropriate answer from the options given below: - True statements about collagen:
A. It is a triple-stranded helical structure, made up of three collagen polypeptide chains, called 'alpha ($\alpha$) chain'
B. It is a repeating tripeptide of Gly-X-Y, where X is often proline, and Y is often 4-hydroxyproline
C. '$\alpha$ chains' are right-handed helix
D. Its glycine residues permit the sharp twisting of the collagen helix
E. Ascorbic acid is required for proline hydroxylation
Choose the correct answer from the options given below: - Choose the correct sequence of events involved in receptor-mediated endocytosis of transferrin:
A. The high pH in the endosome induces transferrin to release its bound iron
B. The low pH in the endosome induces transferrin to completely release its bound iron
C. Iron free transferrin is degraded in lysosome
D. Cell-surface transferrin receptors deliver transferrin with its bound iron to early endosomes by receptor-mediated endocytosis
E. Transferrin receptor along with iron free transferrin is recycled back to the plasma membrane
Choose the correct answer from the options given below: - Choose the correct sequence of events involved in the synthesis of a secretory protein:
A. Signal peptide binds to the interior of the translocon
B. As the signal sequence emerges from the ribosome, it binds to the SRP
C. The SRP-ribosome complex then binds to an SRP receptor situated within the ER membrane
D. Synthesis of the polypeptide begins on a free ribosome
E. After the nascent polypeptide passes into the lumen of the ER, the signal peptide is cleaved by a membrane protein
Choose the correct answer from the options given below: - Correctly arrange the below given Transcription Factors (TFs) as per their involvement in initiation of eukaryotic transcription
A. TFIIB
B. TFIID
C. TFIIE
D. TFIIF
E. TFIIH
Choose the correct answer from the options given below: - Correct sequence of embryonic developmental stages:
A. Blastula
B. Neurula
C. Morula
D. Fertilized egg
E. Gastrula
Choose the correct answer from the options given below: - The ecological niches are characterized into different axes except one:
Important Questions from Mixed Topic (CUET PG)
- Who was the founder of Bolshevik Communist party?
- What is the key guide to statecraft in the realist tradition?
- Chronologically arrange the events in the Cold War period.
A. Berlin Wall is constructed
B. Communist China joins the UN
C. Soviet invasion of Czechoslovakia
D. Berlin Blockade
Choose the correct answer from the options given below: Morgenthau's principles of political realism are:
A. Politics is rooted in permanent and unchanging human nature which is basically self centred, self-regarding and self-interested
B. Politics is an autonomous sphere of action and cannot therefore be reduced to morals
C. International Politics is an arena of conflicting self-interests
D. The ethics of international relations is situational ethics which is very different from private morality
Choose the correct answer from the options given below:Who among the following political thinkers consider the anarchical self help system to be a compelling factor for States to maximise their relative power positions?
