ORGN 249 |
| Robert A. Horton, Karla S. McCain, Joel M. Harris, and Charles B. Grissom. Department of Chemistry, University of Utah, 315 South 1400 East, Salt Lake City, UT 84112-0850 |
| Quantitation of fluorescent cobalamin analogs near the single-molecule level was used to examine the mechanism for the cellular uptake of Vitamin B12 in a living cell. At physiological concentrations of the nutrient, fluorescent cobalamin was detected in the endosome of living NIH 3T3 cells at the level of a few molecules, suggesting that a single molecule of cobalamin is sufficient to stimulate the energy intensive process of receptor-mediated endocytosis. In neoplastic cells, an average of three molecules of fluorescent cobalamin was detected in the endosomes at physiological concentration; reinforcing that cancerous cells sequester more of the nutrient for rapid cellular growth. At higher concentrations, a larger number of cobalamins per endosome is observed, suggesting that the cells express more cellular receptors for cobalamin than the amount of nutrient present at physiological concentrations. This dependence suggests that the cellular concentration of cobalamin is regulated at the organism level rather than at the cellular level. |
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Lipids, Biosynthesis, Enzyme Inhibitors, and Mimetics
8:00 AM-11:20 AM, Tuesday, March 30, 2004 Anaheim Convention Center -- 303D, Oral
Division of Organic Chemistry |