Structural model of ATP-binding proteins associated with cystic fibrosis, multidrug resistance and bacterial transport

Article Abstract:

There is a family of proteins that bind adenosine triphosphate (ATP), a molecule involved in the production of energy, which are also involved in the transport of molecules. This group of proteins includes molecules of bacteria involved in the uptake and export of molecules. In higher organisms, they include genes involved in resistance to multiple types of drugs used in tumor therapy; in resistance to the drug chloroquine in the malarial parasite; the transport of a yeast mating pheromone; and the gene that is defective in cystic fibrosis. Structural models are presented of these ATP-binding transport molecules. In almost 70 percent of the patients with cystic fibrosis, deletions are present in the areas of the gene that are involved in binding and degrading of ATP. Many of the symptoms of cystic fibrosis stem from abnormally thick secretions, especially in the lungs. These symptoms are related to a problem in the transport of chloride ions (electrically charged particles) across cellular membranes. Thus, it was thought that the defective gene in cystic fibrosis might encode a protein that works as a channel that ions pass through. However, some researchers believe that the defective protein in cystic fibrosis is not a channel for chloride molecules. Channels do not require the degradation of ATP. Chloride channels allow the flow of chloride ions in both directions, while the proteins that the gene involved in cystic fibrosis encodes only allow the flow of ions in one direction. Other evidence that indicates the gene does not code for a chloride channel includes: the size of the molecule, which is too large; chloride channels vary in different tissues, but there is only one defective gene in cystic fibrosis; and other characteristic sequences of chloride channels are not present. Therefore, it is thought that the protein is not a chloride channel, but may transport a molecule that regulates a chloride channel. (Consumer Summary produced by Reliance Medical Information, Inc.)

Ion channels

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A frame-shift mutation in the cystic fibrosis gene

Article Abstract:

Cystic fibrosis is a disease that affects 1 in 1,600 Caucasians. It is characterized by abnormally thick mucous secretions by glands in the lungs, which can lead to respiratory infection and death. In the disease state, there is defective regulation of chloride ion transport in the cells of the exocrine glands. The disease is inherited and the defect has been isolated to an area on chromosome 7. The gene coding for the defect has recently been cloned. This gene codes for a protein which is involved in the regulation of ion conduction across the membrane. Mutations of the gene are seen in patients with cystic fibrosis. A deletion of three nucleotides of deoxyribose nucleic acid (DNA) at a particular site of the gene has been found in 70 percent of the patients with cystic fibrosis. A common mutation has not been found in the other cases of cystic fibrosis. A defective cystic fibrosis gene has been characterized in a family in which the genes of the parents do not contain this common deletion. The mother's genes contain two extra nucleotides which are inserted into the cystic fibrosis gene. This gene then codes for a shortened protein which is nonfunctional. The identification of different mutations in the gene that causes cystic fibrosis is important to the understanding of protein function in the disease process, and the types of defects that may result. (Consumer Summary produced by Reliance Medical Information, Inc.)

Lung diseases, Genetic disorders, Human chromosome abnormalities

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Structure of Bordetella pertussis virulence factor P.69 pertactin

Article Abstract:

The Bordetella pertussis P.69 pertactin present in whooping-cough vaccines is a folded monomer containing a 16-stranded parallel beta-helix with a V-shaped cross section. The protein has many protruding loops with domains that confer it biological activity. The 30K carboxy-terminal region, which is necessary for the proper positioning of the P.69 pertactin domain on the cell surface, is located in the outer membrane. The structural characteristics of pertactin are similar to other molecules that show protein-protein interactions.

Analysis, Proteins, Protein structure, Bacterial proteins, Pertussis vaccines

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