Posttranslational modification

(noun)

the chemical modification of a protein after its translation. It is one of the later steps in protein biosynthesis, and thus gene expression, for many proteins.

Related Terms

Examples of Posttranslational modification in the following topics:

  • The Incorporation of Nonstandard Amino Acids

    • Posttranslational modification (PTM) is the chemical modification of a protein after its translation.
    • After translation, the posttranslational modification of amino acids extends the range of functions of the protein by attaching it to other biochemical functional groups (such as acetate, phosphate, various lipids, and carbohydrates), changing the chemical nature of an amino acid (e.g., citrullination), or making structural changes (e.g., formation of disulfide bridges).
    • This amino acid is usually taken off during post-translational modification.
    • Non-standard amino acids that are found in proteins are formed by post-translational modification, which is modification after translation during protein synthesis.
    • Such modifications can also determine the localization of the protein.

  • Vitamins and Amino Acids

    • Vitamin K is a group of structurally similar, fat-soluble vitamins that are needed for the posttranslational modification of certain proteins required for blood coagulation and in metabolic pathways in bone and other tissue .

  • Epigenetic Alterations in Cancer

    • Common in cancer cells, silencing genes, which occur through epigenetic mechanisms, include modifications to histone proteins and DNA.
    • Cancer epigenetics is the study of epigenetic modifications to the genome of cancer cells that do not involve a change in the nucleotide sequence.
    • This combination of DNA methylation and histone deacetylation (epigenetic modifications that lead to gene silencing) is commonly found in cancer.
    • When these modifications occur, the gene present in that chromosomal region is silenced.
    • Mechanisms can include modifications to histone proteins and DNA associated with these silencing genes.

  • Stem Modifications

    • Stem modifications, either aboveground, underground, or aerial, enable plants to survive in particular habitats and environments.
    • A bulb, which functions as an underground storage unit, is a modification of a stem that has the appearance of enlarged fleshy leaves emerging from the stem or surrounding the base of the stem, as seen in the iris .
    • Modifications to the aerial stems, vegetative buds, and floral buds of plants perform functions such as climbing, protection, and synthesis of food vegetative propagation .
    • Aerial modifications of stems include the following:
    • Stem modifications enable plants to thrive in a variety of environments.

  • Knowledge Management and Behavior Modification

    • Knowledge management and behavior modification are tactics employers use to ensure organizational growth and adaptability.
    • In psychology, behavioral modification was made popular by B.
    • Behavioral modification includes altering an individual's behavior through positive and negative reinforcement.
    • Skinner introduced the study of behavior modification, focusing on how animals and humans react to reward and punishment.
    • His theories are still used in behavior modification today.

  • Regulating Protein Activity and Longevity

    • Sometimes these modifications can regulate where a protein is found in the cell; for example, in the nucleus, the cytoplasm, or attached to the plasma membrane.
    • Chemical modifications occur in response to external stimuli such as stress, the lack of nutrients, heat, or ultraviolet light exposure.
    • Because proteins are involved in every stage of gene regulation, the phosphorylation of a protein (depending on the protein that is modified) can alter accessibility to the chromosome, can alter translation (by altering transcription factor binding or function), can change nuclear shuttling (by influencing modifications to the nuclear pore complex), can alter RNA stability (by binding or not binding to the RNA to regulate its stability), can modify translation (increase or decrease), or can change post-translational modifications (add or remove phosphates or other chemical modifications).
    • Another example of chemical modifications affecting protein activity include the addition or removal of methyl groups.
    • Methyl groups are added to proteins via the process of methylation; this is the most common form of post-translational modification.

  • Conclusion

    • All three are associated with the formation of schemata and their modification in order to attain a balanced sense of understanding of the external world.

  • Educational Implications

    • Among the methods derived from behaviorist theory for practical classroom application are contracts, consequences, reinforcement, extinction, and behavior modification.

  • Cancer and Translational Control

    • There are many examples of translational or post-translational modifications of proteins that arise in cancer.
    • Modifications are found in cancer cells from the increased translation of a protein to changes in protein phosphorylation to alternative splice variants of a protein.

  • Epigenetic Control: Regulating Access to Genes within the Chromosome

    • Both the packaging of DNA around histone proteins, as well as chemical modifications to the DNA or proteins, can alter gene expression.
    • This modification changes how the DNA interacts with proteins, including the histone proteins that control access to the region.
    • A gene can be turned on or off depending upon the location and modifications to the histone proteins and DNA.
    • Modifications to the histones and DNA affect nucleosome spacing.
    • Modifications affect nucleosome spacing and gene expression.