Unraveling gene expression

The DNA of a single cell is two to three meters long end-to-end. To fit in the nucleus and function correctly, DNA is packaged around specialized proteins. These DNA-protein complexes are called nucleosomes, and they are ...

Team solves structure of key mTORC1 activator

A research team led by scientists at the Whitehead Institute has described the structure of a key protein complex that helps activate mTORC1, a master growth regulator that enables cells to quickly respond to changing nutrient ...

Sensing sweetness on a molecular level

Whether it's chocolate cake or pasta sauce, the sensation of sweetness plays a major role in the human diet and the perception of other flavors. While a lot is known about the individual proteins that signal "sweet," not ...

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 ...

Physics vs. asthma

A research team from the MIPT Center for Molecular Mechanisms of Aging and Age-Related Diseases has collaborated with colleagues from the U.S., Canada, France, and Germany to determine the spatial structure of the CysLT1 ...

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Protein structure

Proteins are an important class of biological macromolecules present in all biological organisms, made up of such elements as carbon, hydrogen, nitrogen, oxygen, and sulphur. All proteins are polymers of amino acids. The polymers, also known as polypeptides, consist of a sequence of 20 different L-α-amino acids, also referred to as residues. For chains under 40 residues the term peptide is frequently used instead of protein. To be able to perform their biological function, proteins fold into one, or more, specific spatial conformations, driven by a number of noncovalent interactions such as hydrogen bonding, ionic interactions, Van Der Waals forces and hydrophobic packing. In order to understand the functions of proteins at a molecular level, it is often necessary to determine the three dimensional structure of proteins. This is the topic of the scientific field of structural biology, that employs techniques such as X-ray crystallography or NMR spectroscopy, to determine the structure of proteins.

A number of residues are necessary to perform a particular biochemical function, and around 40-50 residues appears to be the lower limit for a functional domain size. Protein sizes range from this lower limit to several thousand residues in multi-functional or structural proteins. However, the current estimate for the average protein length is around 300 residues. Very large aggregates can be formed from protein subunits, for example many thousand actin molecules assemble into a microfilament.

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