Navigation Links
Quaternary structure


In biochemistry, many proteins are actually assemblies of more than one protein molecule, which in the context of the larger assemblage are known as protein subunits. In addition to the tertiary structure of the subunits, multiple-subunit proteins possess a quaternary structure, which is the arrangement into which the subunits assemble. Enzymes composed of subunits with diverse functions are sometimes called holoenzymes, in which some parts may be known as regulatory subunits and the core is often called the catalytic subunit . Examples of proteins with quaternary structure include hemoglobin, DNA polymerase, and ion channels. Other assemblies referred to instead as multiprotein complexes also possess quaternary structure. Examples include nucleosomes and microtubules. Changes in quaternary structure are called conformational changes. It is through such changes, which underlie cooperativity and allostery in "multimeric" enzymes, that many proteins undergo regulation and perform their physiological function.

The above definition follows a classical approach to biochemistry, established at times when the disctinction between a protein and a functional, proteinaceous unit was difficult to elucidate. More recently, people refer to protein-protein interaction when discussing quaternary structure of proteins and consider all assemblies of proteins as protein complexes.

See also: primary structure -- secondary structure -- tertiary structure -- structural biology -- translation


'"/>


(Date:4/11/2017)... -- Research and Markets has announced the addition of ... offering. ... market to grow at a CAGR of 30.37% during the period ... has been prepared based on an in-depth market analysis with inputs ... growth prospects over the coming years. The report also includes a ...
(Date:4/6/2017)... 6, 2017 Forecasts by Product ... Readers, by End-Use (Transportation & Logistics, Government & Public ... & Fossil Generation Facility, Nuclear Power), Industrial, Retail, Business ... Are you looking for a definitive report on ... ...
(Date:4/5/2017)... 4, 2017 KEY FINDINGS The ... at a CAGR of 25.76% during the forecast period ... primary factor for the growth of the stem cell ... MARKET INSIGHTS The global stem cell market ... and geography. The stem cell market of the product ...
Breaking Biology News(10 mins):
Other biology definition