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Archive - Jun 14, 2012

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Atomic-Resolution View Reveals How H. pylori Avoids Stomach Acid

University of Oregon (UO) scientists have discovered how the bacterium Helicobacter pylori navigates through the acidic stomach, opening up new possibilities to inactivate its disease-causing ability without using current strategies that often fail or are discontinued because of side effects. Their report – published online on June 14, 2012 in the journal Structure -- unveils the crystal structure of H. pylori's acid receptor TlpB. The receptor has an external protrusion, identified as a PAS domain, bound by a small molecule called urea and is poised to sense the external environment. TlpB is the first bacterial chemoreceptor of known function shown by crystallography to contain an extracellular PAS domain, the researchers reported. "It is a beautiful structure, and this domain has never been seen before in this class of proteins," said co-author Dr. S. James Remington, professor of physics and member of the UO Institute of Molecular Biology (IMB). Captured at the atomic resolution of 1.38 angstroms, it is the first new, significant structural view in 20 years of the class of receptors used by bacteria to navigate their chemical environment. H. pylori, a Gram-negative bacterium, was first identified in 1982 and shown to be associated with stomach ulcers and stomach cancer. While its mode of transmission is not precisely understood, the bacterium is found in the stomach of half of the people in the world, said co-author Dr. Karen Guillemin, professor of biology and also a member of the IMB. To fight H. pylori infections, patients generally are treated with broad-spectrum antibiotics, but the bacterium is becoming resistant and treatment fails in about 30 percent of cases. As part of the new UO study -- led by postdoctoral researcher Dr. Emily G. Sweeney and doctoral student Dr. J.

Gene May Link Diabetes and Alzheimer's

In recent years, it has become clear that people with diabetes face an ominous prospect – a far greater risk of developing Alzheimer's disease. Now researchers at The City College of New York (CCNY) have shed light on one reason why. Biology Professor Chris Li and her colleagues have discovered that a single gene forms a common link between the two diseases. They found that the gene, known to be present in many Alzheimer's disease cases, affects the insulin pathway. Disruption of this pathway is a hallmark of diabetes. The finding could point to a therapeutic target for both diseases. The researchers report their finding in the June 2012 issue of Genetics. "People with type 2 diabetes have an increased risk of dementia. The insulin pathways are involved in many metabolic processes, including helping to keep the nervous system healthy," said Professor Li, explaining why the link is not far-fetched. Although the cause of Alzheimer's is still unclear, one criterion for diagnosis of the disease after death is the presence of sticky plaques of amyloid protein in decimated portions of patients' brains. Mutations in the human "amyloid precursor protein" (APP) gene, or in genes that process APP, show up in cases of Alzheimer's that run in families. In the study, Professor Li and her colleagues scrutinized a protein called APL-1, made by a gene in the worm Caenorhabditis elegans (C. elegans) that happens to be a perfect stand-in for the human Alzheimer's disease gene. "What we found was that mutations in the worm-equivalent of the APP gene slowed their development, which suggested that some metabolic pathway was disrupted," said Professor Li.