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Theory of Intelligent Design, the best explanation of Origins » Molecular biology of the cell » Post-translational modification

Post-translational modification

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1 Post-translational modification on Fri Aug 07, 2015 6:20 pm

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Post-translational modification 1

The argument of the astounding newly found complex genes
1. The 3-prime untranslated region (3' UTR) gene tails contain a variety of regulatory features. Some of them allow regulatory RNA-binding proteins to attach to the mRNA's tail while others allow small regulatory RNAs—called micro RNAs—to bind. The combination of these bound regulatory molecules fine-tunes and robustly controls genes after the mRNAs are produced. This is a form of regulation called "post-transcriptional," meaning after the mRNA is transcribed.
2. Like the protein-coding areas of the gene, these 3' UTR tails are also alternatively spliced and thus variable. Their size and makeup can vary widely and dynamically between mRNAs from the same gene and between the different cell types in which they are found.
3. While scientists knew that the 3' UTRs of genes had this capability several years ago, they recently discovered that this feature was on a scale much more intricate and massive than they anticipated. In this study, they identified 2035 mouse and 1847 human genes that have 3' UTR tails ranging from 500 to 25,000 bases long. In some cases, they were even longer than the protein-coding areas of the genes themselves. These incredibly long gene tails literally contain hundreds to thousands of genetic switches within each single mRNA.
4. The complexity of genetic control at this level astounds researchers—each network of genes related to a certain cell process is composed of hundreds to thousands of individual genes, each with this type of intricate regulatory set of features. Not only that, but genetic networks in the cell also overlap and function together dynamically, continually, and robustly as part of normal cell physiology.
5. The level of coordination of such genetic complexity is mostly beyond human comprehension and clearly the product of incredible bioengineering.
6. Such complex bioengineering can/could be done only by a superhuman person all men call God.
7. God exists.

Post-translational modification (PTM) refers to the covalent and generally enzymatic modification of proteins during or after protein biosynthesis. Proteins are synthesized by ribosomes translating mRNA into polypeptide chains, which may then undergo PTM to form the mature protein product. PTMs are important components in cell signaling.

Post-translational modification of insulin. At the top, the ribosome translates a mRNA sequence into a protein, insulin, and passes the protein through the endoplasmic reticulum, where it is cut, folded and held in shape by disulfide (-S-S-) bonds. Then the protein passes through the golgi apparatus, where it is packaged into a vesicle. In the vesicle, more parts are cut off, and it turns into mature insulin.
Post-translational modifications can occur on the amino acid side chains or at the protein's C- or N- termini.[1] They can extend the chemical repertoire of the 20 standard amino acids by introducing new functional groups such as phosphate, acetate, amide groups, or methyl groups. Phosphorylation is a very common mechanism for regulating the activity of enzymes and is the most common post-translational modification.[2] Many eukaryotic proteins also have carbohydrate molecules attached to them in a process called glycosylation, which can promote protein folding and improve stability as well as serving regulatory functions. Attachment of lipid molecules, known as lipidation, often targets a protein or part of a protein to the cell membrane.
Other forms of post-translational modification consist of cleaving peptide bonds, as in processing a propeptide to a mature form or removing the initiator methionine residue. The formation of disulfide bonds from cysteine residues may also be referred to as a post-translational modification.[3]:17.6 For instance, the peptide hormone insulin is cut twice after disulfide bonds are formed, and a propeptide is removed from the middle of the chain; the resulting protein consists of two polypeptide chains connected by disulfide bonds.
Some types of post-translational modification are consequences of oxidative stress. Carbonylation is one example that targets the modified protein for degradation and can result in the formation of protein aggregates.[4][5] Specific amino acid modifications can be used as biomarkers indicating oxidative damage.[6]
Sites that often undergo post-translational modification are those that have a functional group that can serve as a nucleophile in the reaction: the hydroxyl groups of serine, threonine, and tyrosine have hydroxyl groups; the amine forms of lysine, arginine, and histidine; the thiolate anion of cysteine; the carboxylates of aspartate and glutamate; and the N- and C-termini. In addition, although the amides of asparagine and glutamine are weak nucleophiles, both can serve as attachment points for glycans. Rarer modifications can occur at oxidized methionines and at some methylenes in side chains.[7]:12–14


1) https://en.wikipedia.org/wiki/Post-translational_modification

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