The objective of this proposal is to elucidate the structure and functions of a membrane domain composed of complexed poly-beta- hydroxybutyrate/calcium polyphosphate (PHB/DaPolyPi) associated with proteins. The complexes are widely distributed in the plasma membranes of prokaryotes, and in the mitochondria, microsomes and plasma membranes of eukaryotes. The isolated complexes conduct calcium currents when incorporated into phospholipid bilayers; in vivo, the complexes are postulated to function in Ca2+ transport, Ca2+ storage and DNA transport. Structural studies will address complexation between Ca2+, PHB and PolyPi, structural uniformity, the conformation of PHB, and the helical pitch and dimensions of the unit cell. Strategies for structural analysis will include 1H and 31P NMR, and FT-IR of solubilized complex; 13C-MAS NMR of complex formed in vitro in membrane vesicles; microscope-aided FT-IR, and X-ray powder diffraction patterns of solid complex. The coordination sphere of Ca2+ in the complex will be investigated through examination of cation selectivity, mobility and replacement employing 45Ca2+ and atomic absorption spectroscopy to analyze cation compositions. The role of the complex in Ca2+ storage and transport will be examined in E. coli cells and membrane vesicles. E. coli become genetically competent in response to a Ca2+ pulse which triggers synthesis of PHB and PolyPi. The polymers sequester Ca2+ to form polymer salt complexes within the membrane. The driving force(s) for PHB/CaPolyPi synthesis and Ca2+ transport will be analyzed using spectrofluorometry, atomic absorption spectroscopy, and radiolabelling methodologies with Ca2+ indicators, ionophores, Ca2+ antagonists, proton-conducting uncouplers, indicators of intracellular pH and membrane potential, and inhibitors of respiration and oxidative phosphorylation. Finally, the changes in intracellular Ca2+ and pH immediately following the Ca2+ pulse will be examined in individual cells using the fluorescent indicators, Indo-1 and SNARF, employing an interactive laser cytometer.

Agency
National Institute of Health (NIH)
Institute
National Institute of General Medical Sciences (NIGMS)
Type
Research Project (R01)
Project #
5R01GM033375-06
Application #
3283038
Study Section
Biophysical Chemistry Study Section (BBCB)
Project Start
1986-04-01
Project End
1995-03-31
Budget Start
1993-04-01
Budget End
1994-03-31
Support Year
6
Fiscal Year
1993
Total Cost
Indirect Cost
Name
Michigan State University
Department
Type
Schools of Arts and Sciences
DUNS #
193247145
City
East Lansing
State
MI
Country
United States
Zip Code
48824
Reusch, Rosetta N (2015) Poly-(R)-3-hydroxybutyrates (PHB) are Atherogenic Components of Lipoprotein Lp(a). Med Hypotheses 85:1041-3
Reusch, Rosetta N (2012) Insights into the structure and assembly of Escherichia coli outer membrane protein A. FEBS J 279:894-909
Reusch, R N (1999) Streptomyces lividans potassium channel contains poly-(R)-3-hydroxybutyrate and inorganic polyphosphate. Biochemistry 38:15666-72
Huang, R; Reusch, R N (1996) Poly(3-hydroxybutyrate) is associated with specific proteins in the cytoplasm and membranes of Escherichia coli. J Biol Chem 271:22196-202
Huang, R; Reusch, R N (1995) Genetic competence in Escherichia coli requires poly-beta-hydroxybutyrate/calcium polyphosphate membrane complexes and certain divalent cations. J Bacteriol 177:486-90
Reusch, R N; Huang, R; Bramble, L L (1995) Poly-3-hydroxybutyrate/polyphosphate complexes form voltage-activated Ca2+ channels in the plasma membranes of Escherichia coli. Biophys J 69:754-66
Reusch, R N (1995) Low molecular weight complexed poly(3-hydroxybutyrate): a dynamic and versatile molecule in vivo. Can J Microbiol 41 Suppl 1:50-4
Castuma, C E; Huang, R; Kornberg, A et al. (1995) Inorganic polyphosphates in the acquisition of competence in Escherichia coli. J Biol Chem 270:12980-3
Seebach, D; Brunner, A; Burger, H M et al. (1994) Isolation and 1H-NMR spectroscopic identification of poly(3-hydroxybutanoate) from prokaryotic and eukaryotic organisms. Determination of the absolute configuration (R) of the monomeric unit 3-hydroxybutanoic acid from Escherichia coli and spinach. Eur J Biochem 224:317-28
Reusch, R N (1992) Biological complexes of poly-beta-hydroxybutyrate. FEMS Microbiol Rev 9:119-29

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