Peptides are stably bound to MHC molecules, and also serve to stabilize the MHC molecule on the cell surface. Once expressed on the surface of host cells, an MHC protein remains stably associated with its bound peptide for several days. This highly stable peptide binding behavior is important because: a) It prevents peptide exchanges on the cell surface, ensuring that peptide:MHC complexes are reliable indicators of the proteins present inside that host cell. b) If the MHC protein lost its peptide it would become unstable, and would be rapidly internalized and degraded. c) Pathogens would otherwise evade the immune response by making decoy peptides that mimic host cell peptides. d) Pathogens would be able to evade the T cell response by making proteases that cleave MHC proteins inducing peptide release. e) Immune responses to infection often induce noxious chemicals that damage surface MHC proteins, and might result in peptide loss.
Nucleotides
It is an organic molecule made up of three basic components- a nitrogenous base, phosphate,and pentose sugar. The nucleotides are important for metabolic reactions andthe formation of DNA (deoxyribonucleic acid) and RNA (ribonucleic acid).
Nucleic Acids
Nucleic acids are essential biomolecules present in prokaryotic and eukaryotic cells and viruses. They carry the genetic information for the synthesis of proteins and cellular replication. The nucleic acids are of two types: deoxyribonucleic acid (DNA) and ribonucleic acid (RNA). The structure of all proteins and ultimately every biomolecule and cellular component is a product of information encoded in the sequence of nucleic acids. Parts of a DNA molecule containing the information needed to synthesize a protein or an RNA are genes. Nucleic acids can store and transmit genetic information from one generation to the next, fundamental to any life form.
Peptides are stably bound to MHC molecules, and also serve to stabilize the MHC molecule on the cell surface. Once expressed on the surface of host cells, an MHC protein remains stably associated with its bound peptide for several days. This highly stable peptide binding behavior is important because:
a) It prevents peptide exchanges on the cell surface, ensuring that peptide:MHC complexes are reliable indicators of the proteins present inside that host cell.
b) If the MHC protein lost its peptide it would become unstable, and would be rapidly internalized and degraded.
c) Pathogens would otherwise evade the immune response by making decoy peptides that mimic host cell peptides.
d) Pathogens would be able to evade the T cell response by making proteases that cleave MHC proteins inducing peptide release.
e) Immune responses to infection often induce noxious chemicals that damage surface MHC proteins, and might result in peptide loss.
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