Cobalamin transport

About: Cobalamin transport is a(n) research topic. Over the lifetime, 72 publication(s) have been published within this topic receiving 3088 citation(s).

Genetic Control by a Metabolite Binding mRNA

Abstract: Messenger RNAs are typically thought of as passive carriers of genetic information that are acted upon by protein- or small RNA-regulatory factors and by ribosomes during the process of translation. We report that the 5′-untranslated sequence of the Escherichia coli btuB mRNA assumes a more proactive role in metabolic monitoring and genetic control. The mRNA serves as a metabolite-sensing genetic switch by selectively binding coenzyme B 12 without the need for proteins. This binding event establishes a distinct RNA structure that is likely to be responsible for inhibition of ribosome binding and consequent reduction in synthesis of the cobalamin transport protein BtuB. This finding, along with related observations, supports the hypothesis that metabolic monitoring through RNA-metabolite interactions is a widespread mechanism of genetic control.

Vitamin B12 (cobalamin) deficiency in elderly patients

Abstract: VITAMIN B12 OR COBALAMIN DEFICIENCY occurs frequently (> 20%) among elderly people, but it is often unrecognized because the clinical manifestations are subtle; they are also potentially serious, particularly from a neuropsychiatric and hematological perspective. Causes of the deficiency include, most frequently, food-cobalamin malabsorption syndrome (> 60% of all cases), pernicious anemia (15%–20% of all cases), insufficent dietary intake and malabsorption. Food-cobalamin malabsorption, which has only recently been identified as a significant cause of cobalamin deficiency among elderly people, is characterized by the inability to release cobalamin from food or a deficiency of intestinal cobalamin transport proteins or both. We review the epidemiology and causes of cobalamin deficiency in elderly people, with an emphasis on food-cobalamin malabsorption syndrome. We also review diagnostic and management strategies for cobalamin deficiency.

Chemistry and biochemistry of B12

Abstract: CHEMISTRY OF B-12. B-12 History (H. Hogenkamp). X-ray Crystallography of B-12 (B. Krautler & C. Kratky). X-Ray Absorption Spectorscopy of B-12: Structural Changes of Intermediate States (M. Chance). Electronic Structure and Spectra of B-12: From Trans Effects to Protein Conformation I (J. Pratt). Electronic Structure and Spectra of B-12: From Trans Effects to Protein Conformation II (J. Pratt). EPR Spectroscopy of B-12-Dependent Enzymes (G. Gerfen). NMR Spectroscopy of B-12 (K. Brown). Vibrational Spectroscopy of B-12 and Related Compounds (L. Marzilli & S. Hirota). Magnetic Field Dependence of Cobalamin Photochemistry and Enzymes (C. Grissom). Stereospecificity of the Coenzyme B-12 Catalyzed Rearrangements and the Role of Negative Catalysis (J. Retey). Modeling the Structure of Cobalt Corrins by Molecular Mechanics and Molecular Dynamics Methods (H. Marques). B-12 Electrochemistry and Organometallic Electrochemical Synthesis (B. Krautler). BIOCHEMISTRY AND BIOLOGY OF B-12. B-12 and Nutrition (S. Stabler). Inborn Errors of Cobalamin Metabolism (D. Rosenblatt & W. Fenton). Diagnostic and Therapeutic Analogs of Cobalamin (H. Hogenkamp, et al.). Intrinsic Factor and Haptocorrin and Their Receptors (D. Alpers & G. Russell-Jones). Transcobalamin II (S. Rothenberg, et al.). Mammalian Receptors of Vitamin B-12-Binding Proteins (S. Moestrup & P. Verroust). Cobalamin Transport in Bacteria (C. Bradbeer). Biosynthesis of B-12 in the Aerobic Organism Pseudomonas denitrificans (A. Battersby & F. Leeper). B-12 Biosynthesis: The Anaerobic Pathway (A. Scott, et al.). Biosynthesis of the 5-6 Dimethylbenzimidazole Moiety of Cobalamin and of the Other Bases Found in Natural Corrinoids (P. Renz). Regulation of Adenosylcobalamin Biosynthesis in Salmonella typhimurium (J. Semerena). X-ray Crystallography of B-12 Enzymes: Methylmalonyl-CoA Mutase and Methionine Synthase (M. Ludwig & P. Evans). The Acetogenic Corriniod Proteins (S. Ragsdale). The Role of Corrinoids in Methanogenesis (K. Sauer & R. Thauer). Methionine Synthase (R. Matthews). Methylmalonyl-CoA Mutase (R. Banerjee & S. Chowdhury). Ribonucleotide Reductases (M. Fontecave & E. Mulliez). Glutamate Mutase and 2-Methyleneglutarate Mutase (W. Buckel, et al.). Diol Dehydrase and Glycerol Dehydrase (T. Toraya). Ethanolamine Ammonia-Lyase (V. Bandarian & G. Reed). Anomutases (P. Frey). Isobutyryl-CoA Mutase (K. Zerbe-Burkhardt, et al.). Reductive Dehalogenases (G. Wohlfarth & G. Diekert).

The proton motive force drives the outer membrane transport of cobalamin in Escherichia coli.

Abstract: Cells of Escherichia coli pump cobalamin (vitamin B12) across their outer membranes into the periplasmic space, and it was concluded previously that this process is potentiated by the proton motive force of the inner membrane. The novelty of such an energy coupling mechanism and its relevance to other outer membrane transport processes have required confirmation of this conclusion by studies with cells in which cobalamin transport is limited to the outer membrane. Accordingly, I have examined the effects of cyanide and of 2,4-dinitrophenol on cobalamin uptake in btuC and atp mutants, which lack inner membrane cobalamin transport and the membrane-bound ATP synthase, respectively. Dinitrophenol eliminated cobalamin transport in all strains, but cyanide inhibited this process only in atp and btuC atp mutant cells, providing conclusive evidence that cobalamin transport across the outer membrane requires specifically the proton motive force of the inner membrane. The coupling of metabolic energy to outer membrane cobalamin transport requires the TonB protein and is stimulated by the ExbB protein. I show here that the tolQ gene product can partly replace the function of the ExbB protein. Cells with mutations in both exbB and tolQ had no measurable cobalamin transport and thus had a phenotype that was essentially the same as TonB-. I conclude that the ExbB protein is a normal component of the energy coupling system for the transport of cobalamin across the outer membrane.

Cobalamin and folate deficiency : Acquired and hereditary disorders in children

Abstract: This review highlights the features of cobalamin and folate deficiency and insufficiency that are particular to children Maternal deficiency of cobalamin and insufficiency or deficiency of folate are the principal causes of deficiencies of these vitamins in the newborn Maternal cobalamin deficiency can be caused by pernicious anemia or postgastrectomy, but most often results from a diet lacking in animal protein The mothers are usually not anemic and failure to thrive and neurological deficits are more common in their infants than is megaloblastic anemia Inborn errors of cobalamin transport and metabolism present with homocystinuria and methylmalonic aciduria, either alone or in combination They share many of the clinical features of nutritional cobalamin deficiency Maternal folate insufficiency results in neural tube defects, fetal loss, prematurity, and fetal growth retardation Inborn errors of folate metabolism are rare, but polymorphisms affecting the gene for methylenetetrahydrofolate reductase (MTHFR) are common and may have significant health implications Elevation of plasma methylmalonic acid (MMA) levels reflects a functional lack of cobalamin, whereas elevated total homocysteine levels are associated with a lack of either folate or cobalamin The determination of these should be part of the investigation of failure to thrive, neurological disorders, and unexplained anemia or cytopenias in children