Related topics: proceedings of the national academy of sciences , cells , genes
Protein
hideProteins (also known as polypeptides) are organic compounds made of amino acids arranged in a linear chain. The amino acids in a polymer chain are joined together by the peptide bonds between the carboxyl and amino groups of adjacent amino acid residues. The sequence of amino acids in a protein is defined by the sequence of a gene, which is encoded in the genetic code. In general, the genetic code specifies 20 standard amino acids, however in certain organisms the genetic code can include selenocysteine — and in certain archaea — pyrrolysine. Shortly after or even during synthesis, the residues in a protein are often chemically modified by post-translational modification, which alter the physical and chemical properties, folding, stability, activity, and ultimately, the function of the proteins. Proteins can also work together to achieve a particular function, and they often associate to form stable complexes.
Like other biological macromolecules such as polysaccharides and nucleic acids, proteins are essential parts of organisms and participate in virtually every process within cells. Many proteins are enzymes that catalyze biochemical reactions and are vital to metabolism. Proteins also have structural or mechanical functions, such as actin and myosin in muscle and the proteins in the cytoskeleton, which form a system of scaffolding that maintains cell shape. Other proteins are important in cell signaling, immune responses, cell adhesion, and the cell cycle. Proteins are also necessary in animals' diets, since animals cannot synthesize all the amino acids they need and must obtain essential amino acids from food. Through the process of digestion, animals break down ingested protein into free amino acids that are then used in metabolism.
Proteins were first described and named by the Swedish chemist Jöns Jakob Berzelius in 1838. However, the central role of proteins in living organisms was not fully appreciated until 1926, when James B. Sumner showed that the enzyme urease was a protein. The first protein to be sequenced was insulin, by Frederick Sanger, who won the Nobel Prize for this achievement in 1958. The first protein structures to be solved were hemoglobin and myoglobin, by Max Perutz and Sir John Cowdery Kendrew, respectively, in 1958. The three-dimensional structures of both proteins were first determined by x-ray diffraction analysis; Perutz and Kendrew shared the 1962 Nobel Prize in Chemistry for these discoveries. Proteins may be purified from other cellular components using a variety of techniques such as ultracentrifugation, precipitation, electrophoresis, and chromatography; the advent of genetic engineering has made possible a number of methods to facilitate purification. Methods commonly used to study protein structure and function include immunohistochemistry, site-directed mutagenesis, and mass spectrometry.
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News tagged with protein
Computational microscope peers into the working ribosome (w/ Video)
Nov 23, 2009 |
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Two new studies reveal in unprecedented detail how the ribosome interacts with other molecules to assemble new proteins and guide them toward their destination in biological cells. The studies used molecular ...
Vibrations key to efficiency of green fluorescent protein
Nov 11, 2009 |
4.5 / 5 (6) |
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University of California, Berkeley, chemists have discovered the secret to the success of a jellyfish protein whose green glow has made it the darling of biologists and the subject of the 2008 Nobel Prize ...
1930s drug slows tumor growth
Medicine & Health / Medications
Nov 06, 2009 |
4.7 / 5 (10) |
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Drugs sometimes have beneficial side effects. A glaucoma treatment causes luscious eyelashes. A blood pressure drug also aids those with a rare genetic disease. The newest surprise discovered by researchers at the Johns ...
Venomous bite: Harmless digestive enzyme evolved into venom in two species
Oct 29, 2009 |
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(PhysOrg.com) -- Biologists have shown that independent but similar molecular changes turned a harmless digestive enzyme into a toxin in two unrelated species -- a shrew and a lizard -- giving each a venomous ...
Alzheimer's researchers find high protein diet shrinks brain
Medicine & Health / Neuroscience
Oct 20, 2009 |
4.7 / 5 (15) |
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One of the many reasons to pick a low-calorie, low-fat diet rich in vegetables, fruits, and fish is that a host of epidemiological studies have suggested that such a diet may delay the onset or slow the progression of Alzheimer's ...
Loss of Tumor-Suppressor and DNA-Maintenance Proteins Causes Tissue Demise, Study Finds
Oct 15, 2009 |
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(PhysOrg.com) -- A study published in the October issue of Nature Genetics demonstrates that loss of the tumor-suppressor protein p53, coupled with elimination of the DNA-maintenance protein ATR, severely disrup ...
Stretching the Golgi: a link between form and function
Oct 15, 2009 |
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A research team at the University of California, San Diego School of Medicine has provided a surprisingly simple explanation for the mechanism and features of the "Golgi apparatus" - a structure that has baffled ...
Magnetic nanotags spot cancer in mice earlier than methods now in clinical use
Nanotechnology / Bio & Medicine
Oct 13, 2009 |
5 / 5 (8) |
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Searching for biomarkers that can warn of diseases such as cancer while they are still in their earliest stage is likely to become far easier thanks to an innovative biosensor chip developed by Stanford University ...
Insulin boost restores muscle growth in elderly
Sep 25, 2009 |
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When most people think of insulin, they think of diabetes — a disease that arises when, for one reason or another, insulin can't do the critical job of helping the body process sugar. But the hormone has another, less well-known ...
Ratchet-like genetic mutations make evolution irreversible
Sep 23, 2009 |
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(PhysOrg.com) -- A University of Oregon research team has found that evolution can never go backwards, because the paths to the genes once present in our ancestors are forever blocked. The findings -- the ...
Rethinking Alzheimer's disease and its treatment targets
Medicine & Health / Neuroscience
Sep 22, 2009 |
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(PhysOrg.com) -- Psychiatry professor George Bartzokis introduces a new theory about the fundamental cause of Alzheimer's and other neurodegenerative diseases.
Researchers discover new antituberculosis compounds
Sep 16, 2009 |
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Attempts to eradicate tuberculosis (TB) are stymied by the fact that the disease-causing bacteria have a sophisticated mechanism for surviving dormant in infected cells. Now, a team of scientists led by researchers from Weill ...
How stem cells make skin
Sep 13, 2009 |
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Stem cells have a unique ability: when they divide, they can either give rise to more stem cells, or to a variety of specialised cell types. In both mice and humans, a layer of cells at the base of the skin ...
Novel 'On-Off Switch' Mechanism Stops Cancer in Its Tracks
Sep 11, 2009 |
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(PhysOrg.com) -- A tiny bit of genetic material with no previously known function may hold the key to stopping the spread of cancer, researchers at Yale School of Medicine and Sichuan University in Chengdu, ...
Tick saliva could hold cancer cure: Brazilian scientists
Aug 28, 2009 |
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It may be one of nature's repulsive little blood-sucking parasites, but the humble tick could yield a future cure for cancers of the skin, liver and pancreas, Brazilian researchers have discovered.
