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The secret of ABC transporters: How do they become the energy engine of the cell?
ABC transporters (ATP-binding cassette transporters) are an indispensable superfamily of transport systems in cells and may be one of the largest and oldest gene families in existence. These transport proteins are present in all living algae, from prokaryotes to humans, demonstrating their importance in the evolutionary history of organisms. ABC transport proteins are mainly divided into input transporters and output transporters, some of which are associated with drug resistance and various genetic diseases.
ABC transport proteins can not only import substances, but also remove toxins and drugs from cells.
Mechanism of ABC transport proteins
ABC transporters transport a variety of substrates across the cell membrane by binding and hydrolyzing ATP to provide the energy needed. Import transporters often live in bacteria and function as mediators of nutrients, such as ions, amino acids, peptides, and sugars, into cells. Export transporters exist in both prokaryotes and eukaryotes and play a role in removing toxins and drugs from cells.
ABC transport proteins in bacteria
Bacterial ABC transporters play critical roles in cell survival, pathogenicity, and virulence. For example, the iron ABC import system is key for pathogens, which use molecules such as siderophores to capture iron coated by high-affinity iron-binding proteins or red blood cells. This type of transport protein is not only involved in the transport of substances, but also involved in the regulation of many physiological processes, including the synthesis of extracellular polysaccharides and the excretion of cytotoxins.
Role in eukaryotes
Although most eukaryotic ABC transport proteins are efflux-type, some transport proteins such as CFTR (cystic fibrosis transmembrane regulator) are not directly involved in the transport of substances, but are important in regulating the functions of other proteins. These transport proteins play key roles in many diseases, particularly those associated with ABC gene polymorphisms, including cystic fibrosis and a range of other genetic disorders.
Mutations in ABC transporters are associated with a variety of human genetic diseases, such as cystic fibrosis and drug-resistant tumors.
Structure and function
All ABC transporters have a uniform structural organization, consisting of four core domains: two transmembrane (T) domains and two cytoplasmic (A) domains. Alternating transitions between these regions are powered by the hydrolysis of ATP. The structure of the T region determines the gene specificity of various ABC transport proteins, which exhibit different affinities for different types of substrates through transport across the cell membrane. This enables ABC transporters to efficiently transport a variety of biomolecules.
The role of ATP
The binding and hydrolysis of ATP are at the core of the operation of ABC transport proteins. When ATP binds to the A region, it can drive structural changes and promote substrate delivery. By hydrolyzing ATP, the transport protein can freely switch between opening and closing, allowing substrates to enter and exit the cell, further enhancing the cell's survivability and adaptability.
Think and execute
With the deepening of research, scientists have gradually understood the multiple roles played by ABC transporters in various biological processes, including the complexity of drug resistance and disease transmission. In the future, what new inspirations or treatment directions might these transport proteins bring us?
