Related topics: cells · genes · cancer · cancer cells · amino acids

The structure of master growth regulator

A team of Whitehead Institute scientists has for the first time revealed the molecular structure of a critical growth regulator bound to its partner proteins, creating a fine-grained view of how they interact to sense nutrient ...

Archaea hold clues to ancient ocean temperatures

Solving a decades-old mystery, Stanford researchers have discovered proteins that enable hardy microbes called archaea to toughen up their membranes when waters are overly warm. Finding these proteins could help scientists ...

Capturing extreme close-ups of cellular gene expression

Scientists studying genetic transcription are gaining new insights into a process that is fundamental to all life. Transcription is the first step in gene expression, the process taking place within all living cells by which ...

Programmable swarmbots help make flexible biological tools

Biomedical engineers at Duke University have developed a new platform to create biologic drugs using specially engineered bacteria that burst and release useful proteins when they sense that their capsule is becoming too ...

Experiments illuminate key component of plants' immune systems

Plants, like humans and animals, have over millions of years evolved complex immune systems that fend off invading pathogens. But unlike many animals, plants lack adaptive immunity conferred by antibodies. This means each ...

Lighting up proteins with Immuno-SABER

To better understand how tissues and organs develop, fail to function, and regenerate over time, researchers would like to visualize their constituent cells' repertoires of molecules within 3-D space. Ambitious efforts like ...

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Protein

Proteins (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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