Streptavidin is a type of bacterial protein that binds to the surface of many different cells. Streptavidin also binds with many substances, such as biotin (one of the B Vitamins) and avidin.
This protein does not have its own genetic information but comes from other cells. It is helpful in research because it can bind with a substance and carry it around more easily than if it was on its own.
The binding between streptavidin and biotin is reversible, which means the two can be separated by heating or adding an acid like hydrochloric acid.
Streptavidin proteins are found in bacteria, fungi, insects, plants, and mammals including humans. They are also found in milk as well as cheese products produced from milk such as Swiss cheese or mozzarella.
Streptavidin has only been found in living things and is very rare, but there are thousands of types of streptavidin that have been discovered since the 1960s. The first type of streptavidin was found on a group of bacteria called hemolytic streptococci.
Streptavidin is used in research because it binds so strongly to other things. When researchers want to study the cell surface, they often add streptavidin and biotin to it. The biotin will bind to the cell.
When they wanted to study a dead or deactivated virus, they would add streptavidin and avidin so that when the virus fell apart, avidin would be able to carry it around without getting stuck in the cell.