In molecular biology the B-box-type zinc finger domain is a short protein domain

Protein domain

A protein domain is a part of protein sequence and structure that can evolve, function, and exist independently of the rest of the protein chain. Each domain forms a compact three-dimensional structure and often can be independently stable and folded. Many proteins consist of several structural...

 of around 40 amino acid residues

Residue (chemistry)

In chemistry, residue is the material remaining after a distillation or an evaporation, or to a portion of a larger molecule, such as a methyl group. It may also refer to the undesired byproducts of a reaction....

 in length. B-box zinc fingers can be divided into two groups, where types 1 and 2 B-box domains differ in their consensus sequence

Consensus sequence

In molecular biology and bioinformatics, consensus sequence refers to the most common nucleotide or amino acid at a particular position after multiple sequences are aligned. A consensus sequence is a way of representing the results of a multiple sequence alignment, where related sequences are...

 and in the spacing of the 7-8 zinc-binding residues. Several proteins contain both types 1 and 2 B-boxes, suggesting some level of cooperativity

Cooperativity

Cooperativity is a phenomenon displayed by enzymes or receptors that have multiple binding sites where the affinity of the binding sites for a ligand is increased, positive cooperativity, or decreased, negative cooperativity, upon the binding of a ligand to a binding site...

 between these two domains. B-box domains are found in over 1500 proteins from a variety of organism

Organism

In biology, an organism is any contiguous living system . In at least some form, all organisms are capable of response to stimuli, reproduction, growth and development, and maintenance of homoeostasis as a stable whole.An organism may either be unicellular or, as in the case of humans, comprise...

s. They are found in TRIM (tripartite motif) proteins that consist of an N-terminal RING finger (originally called an A-box), followed by 1-2 B-box domains and a coiled-coil

Coiled coil

A coiled coil is a structural motif in proteins, in which 2-7 alpha-helices are coiled together like the strands of a rope . Many coiled coil type proteins are involved in important biological functions such as the regulation of gene expression e.g. transcription factors...

 domain (also called RBCC for Ring, B-box, Coiled-Coil). TRIM proteins contain a type 2 B-box domain, and may also contain a type 1 B-box. In proteins that do not contain RING or coiled-coil domains, the B-box domain is primarily type 2. Many type 2 B-box proteins are involved in ubiquitinylation. Proteins containing a B-box zinc finger domain include transcription

Transcription

Transcription may refer to:*Transcription , a business which converts speech into a written or electronic text document*Transcription , software which helps convert speech into text transcript...

 factors, ribonucleoprotein

Ribonucleoprotein

Ribonucleoprotein is a nucleoprotein that contains RNA, i.e. it is an association that combines ribonucleic acid and protein together. A few known examples include the ribosome, the enzyme telomerase, vault ribonucleoproteins, and small nuclear RNPs , which are implicated in pre-mRNA splicing and...

s and proto-oncoproteins; for example, MID1, MID2, TRIM9

TRIM9

Tripartite motif-containing protein 9 is a protein that in humans is encoded by the TRIM9 gene.-Further reading:...

, TNL, TRIM36, TRIM63

TRIM63

E3 ubiquitin-protein ligase TRIM63 is an enzyme that in humans is encoded by the TRIM63 gene.-Interactions:TRIM63 has been shown to interact with Titin, GMEB1 and SUMO2.-Further reading:...

, TRIFIC, NCL1 and CONSTANS-like proteins.

The microtubule-associated E3 ligase MID1 (EC) contains a type 1 B-box zinc finger domain. MID1 specifically binds Alpha-4, which in turn

Turn (biochemistry)

A turn is an element of secondary structure in proteins where the polypeptide chain reverses its overall direction.- Definition :According to the most common definition, a turn is a structural motif where the Cα atoms of two residues separated by few peptide bonds are in close approach A turn is...

 recruits the catalytic subunit of phosphatase

Phosphatase

A phosphatase is an enzyme that removes a phosphate group from its substrate by hydrolysing phosphoric acid monoesters into a phosphate ion and a molecule with a free hydroxyl group . This action is directly opposite to that of phosphorylases and kinases, which attach phosphate groups to their...

 2A (PP2Ac). This complex

Protein complex

A multiprotein complex is a group of two or more associated polypeptide chains. If the different polypeptide chains contain different protein domain, the resulting multiprotein complex can have multiple catalytic functions...

 is required for targeting of PP2Ac for proteasome-mediated degradation

Chemical decomposition

Chemical decomposition, analysis or breakdown is the separation of a chemical compound into elements or simpler compounds. It is sometimes defined as the exact opposite of a chemical synthesis. Chemical decomposition is often an undesired chemical reaction...

. The MID1 B-box coordinates two zinc ion

Ion

An ion is an atom or molecule in which the total number of electrons is not equal to the total number of protons, giving it a net positive or negative electrical charge. The name was given by physicist Michael Faraday for the substances that allow a current to pass between electrodes in a...

s and adopts a beta/beta/alpha cross-brace structure

Protein structure

Proteins are an important class of biological macromolecules present in all organisms. Proteins are polymers of amino acids. Classified by their physical size, proteins are nanoparticles . Each protein polymer – also known as a polypeptide – consists of a sequence formed from 20 possible L-α-amino...

 similar to that of ZZ, PHD, RING and FYVE zinc fingers..

Prokaryotic homologs of the domain are present in several bacterial lineages and methanogenic archaea, and often show fusions to peptidase domains such as the rhomboid-like serine peptidase, and Zn-dependent metallopeptidase. Other versions typically contain transmembrane helices and might also show fusions to domains such as DNAJ, FHA, SH3, WD40 and tetratricopeptide repeats. Together these associations suggest a role for the prokaryotic homologs of the B-box zinc finger domain in proteolytic processing, folding or stability of membrane-associated proteins. The domain architectural syntax is remarkably similar to that seen in prokaryotic homologs of the AN1 zinc finger

AN1 zinc finger

In molecular biology, the AN1-type zinc finger domain, which has a dimetal -bound alpha/beta fold. This domain was first identified as a zinc finger at the C terminus of AN1 , a ubiquitin-like protein in Xenopus laevis...

 and LIM

LIM domain

LIM domains are protein structural domains, composed of two contiguous zinc finger domains, separated by a two-amino acid residue hydrophobic linker. They are named after their initial discovery in the proteins Lin11, Isl-1 & Mec-3. LIM-domain containing proteins have been shown to play roles in...

domains. .