ABCdb is a database for the ATP-binding Cassette (ABC) transporters
encoded by completely sequenced archaeal

Archaea

The Archaea are a group of single-celled microorganisms. A single individual or species from this domain is called an archaeon...

and (eu)bacterial

Bacteria

Bacteria are a large domain of prokaryotic microorganisms. Typically a few micrometres in length, bacteria have a wide range of shapes, ranging from spheres to rods and spirals...

 genomes.

biological function of ABC systems

Most ABC systems function in the transport of a compound across a membrane into the cell (importer)
or to the exterior (exporter), for which the system generates energy by the hydrolysis of adenosine triphosphate (ATP)

Adenosine triphosphate

Adenosine-5'-triphosphate is a multifunctional nucleoside triphosphate used in cells as a coenzyme. It is often called the "molecular unit of currency" of intracellular energy transfer. ATP transports chemical energy within cells for metabolism...

.
The ABC transporters occur in all living organisms.

An ABC transporter system consist minimally of two components: an ATP binding cassette (ABC)

ATP-binding domain of ABC transporters

In molecular biology, ATP-binding domain of ABC transporters is a water-soluble domain of transmembrane ABC transporters.ABC transporters belong to the ATP-Binding Cassette superfamily, which uses the hydrolysis of ATP to translocate a variety of compounds across biological membranes...

 and a TransMembrane domain

Transmembrane domain of ABC transporters

ABC transporter transmembrane domain is main transmembrane structural unit of ATP-binding cassette transporter which consist of six transmembrane domaines...

 (TMD) or Membrane Spanning Domain (MSD).
These are usually separate proteins

Protein

Proteins are biochemical compounds consisting of one or more polypeptides typically folded into a globular or fibrous form, facilitating a biological function. A polypeptide is a single linear polymer chain of amino acids bonded together by peptide bonds between the carboxyl and amino groups of...

 or can occur as protein domains

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...

. A typical ABC transporter is composed of
two Nucleotide Binding Domains

ATP-binding domain of ABC transporters

In molecular biology, ATP-binding domain of ABC transporters is a water-soluble domain of transmembrane ABC transporters.ABC transporters belong to the ATP-Binding Cassette superfamily, which uses the hydrolysis of ATP to translocate a variety of compounds across biological membranes...

 (NBD) that energize transport via ATP hydrolysis and of two Membrane Spanning Domains

Transmembrane domain of ABC transporters

ABC transporter transmembrane domain is main transmembrane structural unit of ATP-binding cassette transporter which consist of six transmembrane domaines...

 (MSD) that act as a membrane channel for the substrate.
Importers require a Solute Binding Protein (SBP) that recognizes and binds the substrate.

The different partners of an ABC system are generally encoded by neighboring genes.

Features

The ABC proteins form a superfamily encoded by large families

Protein family

A protein family is a group of evolutionarily-related proteins, and is often nearly synonymous with gene family. The term protein family should not be confused with family as it is used in taxonomy....

 of paralogous genes.
Sequence analysis

Sequence analysis

In bioinformatics, the term sequence analysis refers to the process of subjecting a DNA, RNA or peptide sequence to any of a wide range of analytical methods to understand its features, function, structure, or evolution. Methodologies used include sequence alignment, searches against biological...

 shows that members of the ABC superfamily may have diverged from common ancestral forms and permits
to organize ABC proteins into sub-families.
The classification of ABC systems into (sub-)families can help to predict which substrates may be transported by the system.

ABCdb is a public resource, from which one can:

• select a strain from the tree of species and view all its ABC systems, classified into (sub-)families.
• for a particular ABC (sub-)family, compare all the proteins of completely sequenced prokaryotes.
• use a sequence and blast it against ABCdb to find annotations for similar proteins

See also

• Membrane transport protein
• TCDB Transporter Classification database
• ABC transporters
• ATP-binding domain of ABC transporters
  ATP-binding domain of ABC transporters
  In molecular biology, ATP-binding domain of ABC transporters is a water-soluble domain of transmembrane ABC transporters.ABC transporters belong to the ATP-Binding Cassette superfamily, which uses the hydrolysis of ATP to translocate a variety of compounds across biological membranes...
  
  
• Transmembrane domain of ABC transporters
  Transmembrane domain of ABC transporters
  ABC transporter transmembrane domain is main transmembrane structural unit of ATP-binding cassette transporter which consist of six transmembrane domaines...