The protein belongs to a class of molecules called membrane transport proteins whose primary job is to move molecules as diverse as nutrients and neurotransmitters across the cell membrane. Membrane transport proteins play such a vital role in the cell that their disruption is thought to be linked to numerous diseases, including depression, stroke and diabetes.

In an article published in the August 1, 2003, issue of the journal Science, a research team led by Howard Hughes Medical Institute investigator H. Ronald Kaback at the University of California, Los Angeles, So Iwata and Jeff Abramson of Imperial College London report that they have solved the three-dimensional structure of the bacterial membrane transport protein lactose permease (LacY). This protein is the most studied representative of the "major facilitator superfamily" of membrane transport proteins, said Kaback. Lac Y uses the energy from an electrochemical proton gradient to drive accumulation of lactose, a sugar, across the cell membrane.

In their studies, the researchers were attempting to create crystals of the LacY protein to analyze using x-ray crystallography. In this widely used analytical technique, x-rays are beamed through purified crystals of a protein. The three-dimensional structure of the crystallized protein is deduced by analyzing the pattern of x-ray diffraction caused by the atoms in the protein.

Kaback said that he and his colleagues spent many frustrating years attempting to crystallize the normal, or "wild-type," LacY protein -- an excruciatingly difficult process given the complexity and "floppi
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Contact: Jim Keeley
keeleyj@hhmi.org
301-215-8858
Howard Hughes Medical Institute
31-Jul-2003