Senior Scientist, Boston Biomedical Research Institute
Adjunct Professor, Institute of General Pathology, Catholic University Medical School, Rome, Italy
Research Associate, Department of Biological Chemistry and Molecular Pharmacology,
Harvard Medical School

B.S., Rensselaer Polytechnic Institute, Physics, 1962
Ph.D., Stanford University, Biophysics and Chemistry, 1967

Structure and function of transport proteins integral to biological membranes. Biochemistry of senescence. Role of superoxide dismutases in cancer.

SUMMARY OF RESEARCH

Inorganic phosphate is one of those anions required for the proper functioning of all cells in the body. More specifically the cell uses it (l) to label metabolic intermediates that are required to extract energy from food (e.g. glucose) in a well-controlled and step-by-step process; (2) as part of the cellular energy currency (adenosine triphosphate or ATP); (3) as an essential element in the intracellular signaling pathways of hormones, cellular growth factors, factors that command cells to die (apoptosis), and in cellular pathways that lead to cancer and other human diseases. Phosphate is also present in the extracellular fluids, e.g. blood. The concentrations of phosphate in the extracellular fluids and in the various compartments within a cell are exquisitely regulated. We have identified a protein that functions as a phosphate transport protein (PTP). It catalyzes the transmembrane transport of inorganic phosphate across an intracellular membrane (mitochondria). This transport is regulated by protons. Amino acid side chains within the PTP specify a gate which is highly specific for inorganic phosphate, i.e. not sulfate or tungstate, two anions very much like inorganic phosphate. The presence of a proton must move one or more of these amino acid side chains by less than one Angstrom (10^-10 meter) to permit a phosphate ion to pass through the membrane. Utilizing bioengineering techniques as well as various instruments and methodologies required for protein structure and function studies, it is expected that the amino acid side chain(s) that (a) is (are) primarily responsible for transmitting this signal to or (b) is (are) located at the phosphate-specific gate can be identified. Two other intrinsic membrane proteins that utilize the sodium ion to signal phosphate to pass through the plasma membrane (membrane separating the cell from the extracellular medium) have more recently been identified by investigators at Eli Lilly (Indianapolis) in brain cells and at the ETH (Zurich) in kidney cells. Much exciting research thus lies thus ahead in elucidating this intramembrane signal pathway.

Wohlrab H. Novel inter- and intra-subunit contacts between transport-relevant residues of the homodimeric mitochondrial phosphate transport protein (PTP). Biochem Biophys Res Commun. 2004;320:685-688.

Phelps A, Wohlrab H. Homodimeric Mitochondrial Phosphate Transport Protein. Transient Subunit/Subunit Contact Site between the Transport Relevant Transmembrane Helices A. Biochemistry. 2004 May 25;43(20):6200-6207.

Berezhna S, Wohlrab H, Champion PM. Resonance Raman investigations of cytochrome c conformational change upon interaction with the membranes of intact and Ca2+-exposed mitochondria. Biochemistry. 2003 May 27;42(20):6149-6158.

Wohlrab H, Annese V, Haefele A. Single replacement constructs of all hydroxyl, basic, and acidic amino acids identify new function and structure-sensitive regions of the mitochondrial phosphate transport protein. Biochemistry. 2002 Mar 5;41(9):3254-3261.

Phelps A, Briggs C, Haefele A, Mincone L, Ligeti E, Wohlrab H. Mitochondrial phosphate transport protein. Reversions of inhibitory conservative mutations identify four helices and a nonhelix protein segment with transmembrane interactions and Asp39, Glu137, and Ser158 as nonessential for transport. Biochemistry. 2001 Feb 20;40(7):2080-2086.

Belenkiy R, Haefele A, Eisen MB, Wohlrab H. The yeast mitochondrial transport proteins: new sequences and consensus residues, lack of direct relation between consensus residues and transmembrane helices, expression patterns of the transport protein genes, and protein-protein interactions with other proteins. Biochim Biophys Acta. 2000 Jul 31;1467(1):207-218.

Briggs C, Mincone L, Wohlrab H. Replacements of basic and hydroxyl amino acids identify structurally and functionally sensitive regions of the mitochondrial phosphate transport protein. Biochemistry. 1999 Apr 20;38(16):5096-5102.

Schroers A, Burkovski A, Wohlrab H, Kramer R. The phosphate carrier from yeast mitochondria. Dimerization is a prerequisite for function.J Biol Chem. 1998 Jun 5;273(23):14269-14276.

Schroers A, Kramer R, Wohlrab H. The reversible antiport-uniport conversion of the phosphate carrier from yeast mitochondria depends on the presence of a single cysteine. J Biol Chem. 1997 Apr 18;272(16):10558-10564.

Phelps A, Briggs C, Mincone L, Wohlrab H. Mitochondrial phosphate transport protein. replacements of glutamic, aspartic, and histidine residues affect transport and protein conformation and point to a coupled proton transport path. Biochemistry. 1996 Aug 20;35(33):10757-10762.

Wohlrab H, Briggs C. Yeast mitochondrial phosphate transport protein expressed in Escherichia coli. Site-directed mutations at threonine-43 and at a similar location in the second tandem repeat (isoleucine-141). Biochemistry. 1994 Aug 16;33(32):9371-9375.