By Roger Segelken
Just because you share the Nobel Prize in chemistry, as Rockefeller University's Roderick MacKinnon did in 2003 for his structural and mechanistic studies of ion channels, don't expect everyone to accept everything you say about ion channels forever after.
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MacKinnon, who spoke on "Potassium Channels" for the 2004 James B. Sumner Lecture Oct. 29 in Cornell's Call Alumni Auditorium, brought an apt audience of students and faculty-researchers up to date on his latest ideas about what regulates the flow of potassium ions through the channels' pores.
Since his 1998 landmark work, when MacKinnon determined the spatial structure of the potassium channel and provided a partial explanation of how ion channels can be opened and closed by different cellular signals, he has focused much of his research on the finer points of voltage-dependent ion channel gating. In last Friday's Sumner Lecture, MacKinnon made good use of graphic illustrations to explain his ideas about what he calls "gating hinges," biotin "tethers" and voltage-sensor "paddles" that move within the electrical fields of membranes and switch channel pores from their open to closed states.
From the questions that followed the lecture, it appeared that most of the audience agreed -- or at least no one quarreled -- with MacKinnon's interpretations. But acceptance by others in his field has not been universal, MacKinnon reported. "There has been criticism. They say, 'He doesn't know thermodynamics.'"
That kind of criticism would have sounded familiar to the lectureship's namesake. The biochemist Sumner (1887-1955) spent his entire professional career at Cornell studying protein structure. But his crowning achievement -- the crystallization of the enzyme urease and demonstration that enzymes are proteins, was greeted in 1926 by skepticism and outright hostility, according to professor of biochemistry George P. Hess, who introduced MacKinnon at the Sumner lecture.
Sumner's Nobel Prize in chemistry, in 1946, quelled the criticism, Hess noted, and by then Sumner's pioneering studies had opened up an entire field of investigation into the structure and function of proteins and enzymes.
MacKinnon, who concluded his talk by crediting all his laboratory assistants by name, acknowledged his scientific debt to three synchrotron radiation facilities, including CHESS (the Cornell High Energy Synchrotron Source). "I am thankful for the synchrotrons' support," said MacKinnon, referring not only to the X-ray crystallography instruments at national-user sites like Cornell's Wilson Synchrotron Laboratory, but also to the technical staff who host visiting scientists.
"I would be out of a job without synchrotrons," he said. "We get our best data from CHESS. It's almost magical."
This year's Class of 1942 James B. Summer Lecture was organized by the Department of Molecular Biology and Genetics and was co-sponsored by the Program in Neuroscience.
At Rockefeller University, MacKinnon is a professor in the laboratory of Molecular Neurobiology and Biophysics and a Howard Hughes Medical Investigator. More details on his ion channel studies can be found at MacKinnon's HHMI Web site: http://www.hhmi.org/research/investigators/mackinnon.html.
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