How nature builds hydrogen-producing enzymes

A team from Ruhr-Universität Bochum and the University of Oxford has discovered how hydrogen-producing enzymes, called hydrogenases, are activated during their biosynthesis. They showed how the cofactor—part of the active ...

New software brings lower-resolution cryo-EM maps into focus

Cryo-electron microscopy is now the most popular method for determining protein structures, which helps researchers develop drugs for different kinds of ailments. Over the last several decades, it has replaced X-ray crystallography ...

Plan B for cholesterol transport

Cholesterol is a vital cell building block in humans and animals, and an integral part of the so-called cell membrane. This boundary layer separates the interior of the cell from the neighboring cells and the surrounding ...

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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