"It's important to note that people have been trying to purify these proteins for a long time. Purification of the first ZIP family member opens the door for detailed structural and functional analysis at the molecular level," Fu said.
Using a fluorescent indicator, Brookhaven's Wei Lin then conducted several measurements to characterize zinc uptake, with attention to changes in zinc concentration, temperature, acidity, and electric charge.
The Brookhaven team found evidence of electrodiffusion. Ions diffuse by moving from a region with a high concentration to one of a lower concentration like diners who relocate from a crowded dining hall to an adjoining, empty coffee room. In electrodiffusion, the diffused ions also change the electric charge of the space that they occupy. The imbalance in charge created by zinc ions moving into the cell builds during zinc uptake and acts against the concentration gradient, eventually causing zinc uptake to stop.
Based in part on the studies of similar metal-specific proteins, Fu and his colleagues have postulated that the ZIP protein allows zinc ion diffusion by providing an opening that is specifically shaped for zinc coordination chemistry. This hypothesis will eventually be confirmed in studies that crystallize and examine the ZIP protein at the atomic level.
"We are driven by our curiosity we want to know how this works," Fu said.
Aside from satisfying scientific curiosity, this understanding could have a big impact. Zinc uptake at the cellular level is implicated in a range of biomedical and energy research. For example, in green plants, carbonic acid is converted to CO2 in a chemical reaction t
|Contact: Karen McNulty Walsh|
DOE/Brookhaven National Laboratory