In molecular biology, ADF-H domain (actin-depolymerising factor homology domain) is an approximately 150

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 a ...

motif that is present in three phylogenetically distinct classes of

eukaryotic Eukaryotes () are organisms whose Cell (biology), cells have a cell nucleus, nucleus. All animals, plants, fungi, and many unicellular organisms, are Eukaryotes. They belong to the group of organisms Eukaryota or Eukarya, which is one of the ...

actin-binding proteins. *ADF/cofilins, which include ADF,

cofilin ADF/cofilin is a family of actin-binding proteins associated with the rapid depolymerization of actin microfilaments that give actin its characteristic dynamic instability. This dynamic instability is central to actin's role in muscle contractio ...

destrin Destrin or DSTN (also known as actin depolymerizing factor or ADF) is a protein which in humans is encoded by the ''DSTN'' gene. Destrin is a component protein in microfilaments. The product of this gene belongs to the actin-binding proteins ADF ( ...

, actophorin, coactosin, depactin and glia maturation factors (GMFs) beta and gamma. ADF/cofilins are small actin-binding

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, res ...

s composed of a single ADF-H domain. They

bind BIND () is a suite of software for interacting with the Domain Name System (DNS). Its most prominent component, named (pronounced ''name-dee'': , short for ''name daemon''), performs both of the main DNS server roles, acting as an authoritative ...

both actin-monomers and filaments and promote rapid filament turnover in cells by depolymerising/fragmenting actin filaments. ADF/cofilins bind ADP-actin with higher affinity than ATP-actin and inhibit the spontaneous

nucleotide Nucleotides are organic molecules consisting of a nucleoside and a phosphate. They serve as monomeric units of the nucleic acid polymers – deoxyribonucleic acid (DNA) and ribonucleic acid (RNA), both of which are essential biomolecule ...

exchange on

actin Actin is a family of globular multi-functional proteins that form microfilaments in the cytoskeleton, and the thin filaments in muscle fibrils. It is found in essentially all eukaryotic cells, where it may be present at a concentration of ov ...

monomer In chemistry, a monomer ( ; '' mono-'', "one" + ''-mer'', "part") is a molecule that can react together with other monomer molecules to form a larger polymer chain or three-dimensional network in a process called polymerization. Classification ...

s * Twinfilins, which are actin monomer-binding

s that are composed of two ADF-H domains *Abp1/Drebrins, which are relatively large proteins composed of an N-terminal ADF-H domain followed by a variable region and a C-terminal

SH3 domain The SRC Homology 3 Domain (or SH3 domain) is a small protein domain of about 60 amino acid residues. Initially, SH3 was described as a conserved sequence in the viral adaptor protein v-Crk. This domain is also present in the molecules of phos ...

. Abp1/Drebrins

interact Advocates for Informed Choice, dba interACT or interACT Advocates for Intersex Youth, is a 501(c)(3) nonprofit organization using innovative strategies to advocate for the legal and human rights of children with intersex traits. The organizati ...

only with actin filaments and do not promote filament depolymerisation or fragmentation. Although these proteins are biochemically distinct and play different roles in actin dynamics, they all appear to use the ADF-H domain for their interactions with actin. The ADF-H domain consists of a six-stranded mixed

beta-sheet The beta sheet, (β-sheet) (also β-pleated sheet) is a common motif of the regular protein secondary structure. Beta sheets consist of beta strands (β-strands) connected laterally by at least two or three backbone hydrogen bonds, forming a ge ...

in which the four central strands (beta2-beta5) are anti-parallel and the two edge strands (beta1 and beta6) run parallel with the neighbouring strands. The sheet is surrounded by two

alpha-helices The alpha helix (α-helix) is a common motif in the secondary structure of proteins and is a right hand-helix conformation in which every backbone N−H group hydrogen bonds to the backbone C=O group of the amino acid located four residues ear ...

on each side .

References

{{InterPro content, IPR002108 Protein domains