Biomedical Engineering Reference
In-Depth Information
works—what component does what and how. With a growing
understanding of how proteins work, physicians and scientists such
as Banting sought to replace a missing or malfunctioning protein.
An animal protein could not correct every missing or defective
protein in a human patient, however, because, in some cases, the
animal version of the protein is too different in shape to fit correctly
into the human cell receptor. Pig insulin differs from human insulin
by only 1 of its 51 amino acids, so it works well on human cells. Not
every animal protein is as similar to its human counterpart, though,
so deliberately producing the human protein itself seemed like a
good idea. The recombinant DNA methods that were developed
beginning in the 1970s made that possible.
Another Kind of Factory: Producing Sugars
Some human proteins produced in a bacterium will not work even
if the amino acid sequence is identical to the human protein. This
is because our cells, and the cells of plants, animals, and yeast,
add sugars to most of the proteins they produce. There are many
different kinds of sugar molecules, and the type of sugar added and
the place in the cell and on the protein where the sugars are added
vary among cells for different species. If the correct sugars are not
on the correct spot on the protein, the protein may not fit into the
receptor pocket correctly, and thus not have the desired effect. Also,
without the added sugars, the enzymes in our blood may destroy
the protein before it can get to the appropriate spot to bind to the
correct receptor.
One way to overcome this problem is to make the protein in
cells from organisms that do add sugars to their proteins, as our
cells do. To accomplish this, scientists have developed ways to put
the genetic information for the drug protein into an animal, plant,
insect, or yeast cell so that the protein will be made with sugar
added. But because different types of cells and even the same cells
under different conditions may attach different sugars in different
Search WWH ::




Custom Search