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Protein quaternary structure describes the number and arrangement of multiple folded protein subunits in a multi-subunit complex. It includes organizations from simple dimers to large homooligomers and complexes with defined or variable numbers of subunits. [1] In contrast to the first three levels of protein structure, not all proteins will ...
Quaternary structure is the three-dimensional structure consisting of the aggregation of two or more individual polypeptide chains (subunits) that operate as a single functional unit . The resulting multimer is stabilized by the same non-covalent interactions and disulfide bonds as in tertiary structure.
The image above contains clickable links This diagram (which is interactive) of protein structure uses PCNA as an example. (The image above contains clickable links Interactive image of nucleic acid structure (primary, secondary, tertiary, and quaternary) using DNA helices and examples from the VS ribozyme and telomerase and nucleosome
Discovering the tertiary structure of a protein, or the quaternary structure of its complexes, can provide important clues about how the protein performs its function and how it can be affected, i.e. in drug design. As proteins are too small to be seen under a light microscope, other methods have to be employed to determine their structure.
Hydrogen bonding networks between subunits has been shown to be important for the stability of the tetrameric quaternary protein structure.For example, a study of SDH which used diverse methods such as protein sequence alignments, structural comparisons, energy calculations, gel filtration experiments and enzyme kinetics experiments, could reveal an important hydrogen bonding network which ...
Tertiary structure may give way to the formation of quaternary structure in some proteins, which usually involves the "assembly" or "coassembly" of subunits that have already folded; in other words, multiple polypeptide chains could interact to form a fully functional quaternary protein. [12]
Protein complexes are distinct from multidomain enzymes, in which multiple catalytic domains are found in a single polypeptide chain. [1] Protein complexes are a form of quaternary structure. Proteins in a protein complex are linked by non-covalent protein–protein interactions. These complexes are a cornerstone of many (if not most ...
In biochemistry, a protein dimer is a macromolecular complex or multimer formed by two protein monomers, or single proteins, which are usually non-covalently bound. Many macromolecules, such as proteins or nucleic acids, form dimers. The word dimer has roots meaning "two parts", di-+ -mer. A protein dimer is a type of protein quaternary structure.