Galactose-1-phosphate uridylyltransferase 1GUP

biochemistry Biochemistry or biological chemistry is the study of chemical processes within and relating to living organisms. A sub-discipline of both chemistry and biology, biochemistry may be divided into three fields: structural biology, enzymology ...

, a protein dimer is a macromolecular complex formed by two protein monomers, or single proteins, which are usually non-covalently bound. Many

macromolecule A macromolecule is a very large molecule important to biophysical processes, such as a protein or nucleic acid. It is composed of thousands of covalently bonded atoms. Many macromolecules are polymers of smaller molecules called monomers. ...

s, such as

protein Proteins are large biomolecules and macromolecules that comprise one or more long chains of amino acid residues. Proteins perform a vast array of functions within organisms, including catalysing metabolic reactions, DNA replication, respon ...

s or

nucleic acid Nucleic acids are biopolymers, macromolecules, essential to all known forms of life. They are composed of nucleotides, which are the monomers made of three components: a 5-carbon sugar, a phosphate group and a nitrogenous base. The two main ...

s, form dimers. The word ''dimer'' has roots meaning "two parts", ''

di- Numeral or number prefixes are prefixes derived from numerals or occasionally other numbers. In English and many other languages, they are used to coin numerous series of words. For example: * unicycle, bicycle, tricycle (1-cycle, 2-cycle, 3-cyc ...

'' + '' -mer''. A protein dimer is a type of protein quaternary structure. A protein homodimer is formed by two identical

s. A protein heterodimer is formed by two different proteins. Most protein dimers in biochemistry are not connected by covalent bonds. An example of a non-covalent heterodimer is the enzyme reverse transcriptase, which is composed of two different

amino acid Amino acids are organic compounds that contain both amino and carboxylic acid functional groups. Although hundreds of amino acids exist in nature, by far the most important are the alpha-amino acids, which comprise proteins. Only 22 alpha ...

chains. An exception is dimers that are linked by disulfide bridges such as the homodimeric protein NEMO. Some proteins contain specialized domains to ensure dimerization (dimerization domains) and specificity. The G protein-coupled cannabinoid receptors have the ability to form both homo- and heterodimers with several types of receptors such as mu-opioid,

dopamine Dopamine (DA, a contraction of 3,4-dihydroxyphenethylamine) is a neuromodulatory molecule that plays several important roles in cells. It is an organic chemical of the catecholamine and phenethylamine families. Dopamine constitutes about 8 ...

and adenosine A2 receptors.

Examples

Transcription factor In molecular biology, a transcription factor (TF) (or sequence-specific DNA-binding factor) is a protein that controls the rate of transcription of genetic information from DNA to messenger RNA, by binding to a specific DNA sequence. The fu ...

s ** Leucine zipper motif proteins *

14-3-3 protein 14-3-3 proteins are a family of conserved regulatory molecules that are expressed in all eukaryotic cells. 14-3-3 proteins have the ability to bind a multitude of functionally diverse signaling proteins, including kinases, phosphatases, and trans ...

s * Variable surface glycoproteins of the ''Trypanosoma'' parasite * Tubulin * Some clotting factors ** Factor XI ** Factor XIII **

Fibrin Fibrin (also called Factor Ia) is a fibrous, non-globular protein involved in the clotting of blood. It is formed by the action of the protease thrombin on fibrinogen, which causes it to polymerize. The polymerized fibrin, together with pla ...

ogen * Some receptors **

Nuclear receptor In the field of molecular biology, nuclear receptors are a class of proteins responsible for sensing steroids, thyroid hormones, vitamins, and certain other molecules. These receptors work with other proteins to regulate the expression of s ...

s **

G protein-coupled receptor G protein-coupled receptors (GPCRs), also known as seven-(pass)-transmembrane domain receptors, 7TM receptors, heptahelical receptors, serpentine receptors, and G protein-linked receptors (GPLR), form a large group of evolutionarily-related p ...

s **

G protein G proteins, also known as guanine nucleotide-binding proteins, are a family of proteins that act as molecular switches inside cells, and are involved in transmitting signals from a variety of stimuli outside a cell to its interior. Their ...

βγ-subunit dimer **

Toll-like receptor Toll-like receptors (TLRs) are a class of proteins that play a key role in the innate immune system. They are single-pass membrane-spanning receptors usually expressed on sentinel cells such as macrophages and dendritic cells, that recogniz ...

** Receptor tyrosine kinases * Some enzymes ** Type II restriction enzymes ** Triosephosphateisomerase (TIM) ** Alcohol dehydrogenase

Alkaline phosphatase

''E. coli'' alkaline phosphatase, a dimer enzyme, exhibits

intragenic complementation Epistasis is a phenomenon in genetics in which the effect of a gene mutation is dependent on the presence or absence of mutations in one or more other genes, respectively termed modifier genes. In other words, the effect of the mutation is ...

. That is, when particular

mutant In biology, and especially in genetics, a mutant is an organism or a new genetic character arising or resulting from an instance of mutation, which is generally an alteration of the DNA sequence of the genome or chromosome of an organism. It ...

versions of alkaline phosphatase were combined, the heterodimeric enzymes formed as a result exhibited a higher level of activity than would be expected based on the relative activities of the parental enzymes. These findings indicated that the dimer structure of the ''E. coli'' alkaline phosphatase allows cooperative interactions between the constituent mutant monomers that can generate a more functional form of the holoenzyme.

References

{{DEFAULTSORT:Protein dimer Protein structure Dimers (chemistry) Protein complexes

Examples

Alkaline phosphatase

See also

References