Welcome to my research page

One day, we will know all of the cell.

To understand our cells .. is to understand our selves.

 


 Cells:   The final frontier.
These are the voyages of the biochemistry graduate student.
Our five year (continuing?) mission:
  To explore the furthest depths of the cell,
  To seek out new enzymes and signal cascades,
  To bodly go where no Ph.D. student has gone before.

Introduction

  The easiest way to explain what it is that I do is to first describe the big picture. Collectively, we are trying to find out everything that goes on in the cell.   All the research that we do hopefully adds a piece to the puzzle that is the cell.   In my little corner of the cell, we are studying a process called protein glycosylation, which is the linking of sugar molecules to proteins.   Proteins have many functions within a cell.   Adding sugars to proteins may alter the characteristics of a protein so that it folds differently into its three dimensional structure.  Or they may change the behavior of the protein (like activating or inactivating it).   Sugars on proteins may affect the localization of a protein in a cell or how long a protein "survives".   Sugars (also called carbohydrates) are extremely diverse structures in biology. The study of carbohydrates of cells is called 'Glycobiology'.   There are many types of sugars in cells, and they have different functions.   When we discover a new type of sugar structure, we try to find out everything about it - How it is made and what it does.

The Specifics

  I am studying a unique protein modification called O-linked fucose.   O-linked fucose consists of the sugar, fucose, directly attached to protein through the hydroxyl group of either serine or threonine.   It was discovered within this decade and has been found on a small number of proteins involved in blood coagulation and fibrinolysis, including the proteins: tissue plasminogen activator, urokinase, and clotting factors VII, IX, and XII.   The modification is found on epidermal growth factor-like (EGF) modules (which are small looped bundles within some proteins) which contain the consensus sequence for O-linked fucose addition: CXXGGS/TC.   Although the actual number of proteins identified with the O-linked fucose modification is small, a database search reveals that numerous secreted and cell-surface proteins from nematodes to insects to humans contain the consensus sequence for the addition of the sugar, O-linked fucose, meaning that this sugar modification appears to be conserved through evolution.

  Although fucose is typically thought of as a terminal sugar (ie. the endpoint of an oligosaccharide), we have shown that proteins from Chinese hamster ovary cells contain an elongated form of O-linked fucose.   A glucose residue may be added to O-linked fucose on specific O-linked fucose-containing protein species.   After identifying this novel structure, we set out to find the enzyme involved in its synthesis.   The enzyme which attaches fucose to protein, the peptide O-fucosyltransferase, has been identified and characterized recently by Dr. Yang Wang at Genentech, Inc.   We have identified and characterized an enzyme activity in the Chinese hamster ovary cells grown in culture (as well as in human, mouse, rat, and chicken culture cells) which adds the glucose to O-linked fucose.

  Our current goals are to purify this enzyme, identify proteins containing the disaccharide (glucosylfucose) structure, and hopefully get some insights into the function or role that this sugar plays on protein.

  All other projects regarding O-linked fucose and the glycosylation of EGF modules are currently guarded as Top Secret.
To obtain a special access permit, contact the Haltiwanger Lab, or The National Glycobiology Security Council (NGSC) - Department for Access to the Network (DAN).

 

References:

  Moloney, D.J. and Haltiwanger, R.S. (1999) The O-linked fucose glycosylation pathway: Identification and characterization of a uridine diphosphoglucose: fucose-beta-1,3 glucosyltransferase activtity from Chinese hamster ovary cells. Glycobiology 9, 679-687.

  Moloney, D.J., Lin A.I., and Haltiwanger, R.S. (1997) The O-linked fucose glycosylation pathway: Evidence for protein-specific elongation of O-linked fucose in Chinese hamster ovary cells. J. Biol. Chem. 272,19046-19050.

  Haltiwanger, R.S., Busby, S., Grove, K., Li, S., Mason, D., Medina, L., Moloney, D., Philipsberg, G., and Scartozzi, R. (1997) O-glycosylation of nuclear and cytoplasmic proteins: Regulation analogous to phosphorylation?Biochem. Biophys. Res. Comm. 231,237-242.

 

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Created by Daniel J. Moloney
Equinox publishing @1999

Last modified 10/19/99

send email to : dmoloney@ic.sunysb.edu