|
|
|
| Current Issue |
|
|
| Resources |
|
|
|
The New World of Glycoproteins
| Article
# : |
19720 |
|
|
Section : |
NATURAL SCIENCE
|
| Issue
Date : |
9 / 1991 |
2,939 Words |
| Author
: |
Gerald R. Campbell
Gerald R. Campbell is a research scientist and science writer
in Saint Louis, Missouri. |
What is in a horse? Or a turtle, an oak tree, or a newborn human baby? All life is basically composed of the same elemental atoms that combine to form the molecules of life--especially proteins, sugars, fats and oils, nucleic acids, and water. These foundation insights have been taught to millions in high school and college biology courses.
Yet, many phenomena in living organisms have continued to challenge scientific investigators. One set of unanswered questions has dealt with the way proteins could achieve their diverse functions.
What keeps the proteins on two cells stuck to each other in one case, but prevents other proteins from sticking to them in another? What plays traffic cop for the hundreds of proteins made by complex cells, steering each to its appropriate target? What keeps some of those proteins floating free in the bloodstream for days, but then with one tiny chemical change causes them to be removed from the bloodstream within minutes?
In all cases, the answer is sugars, which are attached to protein molecules, forming macromolecules called glycoproteins. In fact, most proteins made by eukaryotic (nucleated) cells have complex strings of sugars (carbohydrates) attached.
Glycoproteins were dismissed as unimportant just twenty years ago, partly due to the lack of any clue about why the carbohydrates were present on glycoproteins, and partly because glycoproteins were extremely difficult to work with. It is difficult to work with glycoproteins because (1) they consist of two chemically different groups, proteins and carbohydrates (sugars and sugar polymers), and (2) they are very complex [see "Glyco + Protein = Complexity," p.293]. Because proteins and carbohydrates are so different chemically, any attempt to study one frequently results in the destruction of the other; having to pick one to study, most scientists chose to work on the supposedly more important protein portion.
Some functions known, others still unknown
While the biological functions of some glycoproteins have been discovered, there are others that remain a mystery. In part this is due to the late start of research into the functions of glycoproteins, which in turn was because of misleading "in vitro" experiments (performed outside the living organism) conducted in the 1960s and 1970s. These experiments suggested that soluble blood glycoproteins worked
...
Read Full Article
Look for this article in Ask.com
|
|
