Selenophosphate (SeP), the energy-rich Se compound required for synthesis of many selenoenzymes is formed by selenophosphate synthetase (SPS) from ATP and an inorganic form of Se. The participation of specialized selenium delivery proteins to furnish Se specifically to SPS serves to maintain intracellular levels of selenium below toxic levels. Certain classes of delivery proteins that can utilize selenocysteine as substrate, selenocysteine lyases, include three NifS related proteins from E. coli and one from Methanococcus vannielii, an anaerobic organism that is particularly rich in selenoenzymes and factors required for selenoprotein biosynthesis. A selenium-binding protein that reacts with inorganic selenium also was isolated from M. vannielii. The gene encoding this protein was isolated, cloned, and expressed in E. coli by Dr. William Self. The expressed protein, obtained in good yield and identical to native protein, binds selenite. Antibodies to this protein allow its ready isolation from M. vannielii crude extracts. To date no stabilized forms or adducts of the highly oxygen-labile selenophosphate have been found either in mammalian or bacterial systems. Either this general selenium donor compound must be synthesized in situ wherever needed or some transportable form should exist. Based on properties of a thiophosphate-menadione addition product that we prepared previously, a corresponding derivative of selenophosphate might exist. The possibility that a unique menadione-dependent paranitrophenyl phosphatase could have a role in its formation is being examined by Dr. Lara Campbell. This enzyme is relatively abundant in certain selenium-rich anaerobic bacteria and has no known biological function. As a continuation of studies on human thioredoxin reductase, Dr. Shoshana Bar-Noy tested the feasibility of producing C-terminal extensions to allow separation of the active selenocysteine-containing enzyme from prematurely terminated inactive forms. Unfortunately, Dr. Bar-Noy completed her allowed stay at NIH and left the laboratory on June 1, 2002, without finishing the project. A group of selenium-dependent molybdopterin hydroxylases present in some anaerobic bacteria contain an unidentified cofactor form of selenium. A purine hydroxylase discovered and studied by Dr. William Self is an excellent system for study of this selenium cofactor, particularly as regards its mode of synthesis and mechanism of addition to these enzymes. Model donor compounds, such as a lipoic acid-selenium adduct, are prepared by Dr. Self and tested. A collaborative research effort initiated by Dr. Gerard Lacourciere on various selenium delivery proteins that are detected as bacterial gene products by other investigators was continued by Dr. Matt Wolfe after Dr. Lacourciere left NIH on April 12, 2002. These are characterized as to ability to furnish atomic selenium for selenophosphate synthetase and types of interactions with the enzyme.

Agency
National Institute of Health (NIH)
Institute
National Heart, Lung, and Blood Institute (NHLBI)
Type
Intramural Research (Z01)
Project #
1Z01HL000205-47
Application #
6675565
Study Section
(LB)
Project Start
Project End
Budget Start
Budget End
Support Year
47
Fiscal Year
2002
Total Cost
Indirect Cost
Name
U.S. National Heart Lung and Blood Inst
Department
Type
DUNS #
City
State
Country
United States
Zip Code
Suzuki, Motoshi; Lee, Duck-Yeon; Inyamah, Nwakaego et al. (2008) Solution NMR structure of selenium-binding protein from Methanococcus vannielii. J Biol Chem 283:25936-43
Ogasawara, Yuki; Lacourciere, Gerard M; Ishii, Kazuyuki et al. (2005) Characterization of potential selenium-binding proteins in the selenophosphate synthetase system. Proc Natl Acad Sci U S A 102:1012-6
Stadtman, Thressa C (2005) Selenoproteins--tracing the role of a trace element in protein function. PLoS Biol 3:e421
Patteson, Kemberly G; Trivedi, Neel; Stadtman, Thressa C (2005) Methanococcus vannielii selenium-binding protein (SeBP): chemical reactivity of recombinant SeBP produced in Escherichia coli. Proc Natl Acad Sci U S A 102:12029-34
Tamura, Takashi; Yamamoto, Shinpei; Takahata, Muneaki et al. (2004) Selenophosphate synthetase genes from lung adenocarcinoma cells: Sps1 for recycling L-selenocysteine and Sps2 for selenite assimilation. Proc Natl Acad Sci U S A 101:16162-7
Stadtman, Thressa (2004) Methanococcus vannielii selenium metabolism: purification and N-terminal amino acid sequences of a novel selenium-binding protein and selenocysteine lyase. IUBMB Life 56:427-31
Self, William T; Pierce, Renee; Stadtman, T C (2004) Cloning and heterologous expression of a Methanococcus vannielii gene encoding a selenium-binding protein. IUBMB Life 56:501-7
Wolfe, Matt D; Ahmed, Farzana; Lacourciere, Gerard M et al. (2004) Functional diversity of the rhodanese homology domain: the Escherichia coli ybbB gene encodes a selenophosphate-dependent tRNA 2-selenouridine synthase. J Biol Chem 279:1801-9
Self, William T; Wolfe, Matt D; Stadtman, Thressa C (2003) Cofactor determination and spectroscopic characterization of the selenium-dependent purine hydroxylase from Clostridium purinolyticum. Biochemistry 42:11382-90
Stadtman, Thressa Campbell (2002) Discoveries of vitamin B12 and selenium enzymes. Annu Rev Biochem 71:1-16

Showing the most recent 10 out of 23 publications