Makowski and his colleagues were also surprised to discover that environmental conditions strongly influence which state in this ensemble of conformations a protein prefers to enter. Most of a proteins common configurations have a functional purpose, he said, as it is not likely to twist itself into something completely irrelevant to its function.
For example, one of the five proteins examined in the study, hemoglobin, has two favored conformations: one in which it binds oxygen very readily and one in which it does not. When hemoglobin is placed in a solution that contains a great deal of available oxygen, it spends most of the time in the former state, while if oxygen is not available, it usually flips into the latter. We now know that in dilute solutions, hemoglobin actually can take on both conformations - even in the absence of oxygen, he said.
By keeping all of the environmental factors the same save for the protein concentration in the solution, Makowski and his team discovered another surprising result. Scientists had known for many years that when proteins are too concentrated, they aggregate and fall out of solution. However, biochemists previously had difficulty explaining why a similar effect also occurs in overly dilute solutions.
Proteins have hydrophobic or water-hating core regions that try to avoid touching water if at all possible. Because of this characteristic, proteins will rearrange themselves to protect these r
|Contact: Steve McGregor|
DOE/Argonne National Laboratory