ZINC AND BRAIN

[Guest guest]

Zinc Found To Be Integral Part Of Brain

Communication Channels

LA JOLLA, CALIF. January 6, 1999 -- Zinc has long

been recognized as an

essential trace element, and a current study led by

Salk Institute investigators

shows it to be an integral part of ion channels,

structures that regulate

communication among nerve cells.

The study, which appears in the current issue of

Nature Structural Biology,

may explain why zinc deficiency has been linked to

cognitive impairment.

" We don't know yet what zinc is doing, but it is

definitely a component in these

essential structures, " said Senyon Choe, an assistant

professor at The Salk

Institute for Biological Studies and senior author on

the study. " And it was

surprising--at first we tried to disregard it,

thinking it must be a contaminant,

but, of course as you try to disprove it, it keeps

coming back. "

Ion channels are important " gatekeepers " that

regulate the way ions such as

calcium and potassium flow into and out of cells.

Their flux is necessary for

important neuronal processes. Calcium streams into

brain cells and helps to

initiate changes that accompany learning.

Abnormalities in potassium channels

have been found in some epileptics and in persons

with both insulin-resistance

and mobility disorders.

In the current study, Choe and his colleagues used

X-ray crystallography to

resolve the structures of four potassium channels

from the sea slug Aplysia.

The channels, called Shaw, Shab, Shal and Shaker,

represent the four classes

of potassium channels found in all higher organisms,

including humans. With

the exception of Shaker, all of the channels

contained four zinc atoms in

analogous positions.

" Each channel resembles a funnel, " said Choe, " and

the zinc elements ring the

end that empties into the cell's interior. "

Neuroscientists have known for decades that dyes that

bind to zinc stain brain

cells in unique patterns, indicating that zinc should

have a role in brain function

and studies have shown that zinc can enhance learning

in undernourished

children. The nature of zinc's organization in the

brain, however, had been

unclear.

" Now we know that zinc is embedded within structures

that are absolutely

critical for nerve cell activity, " said Choe.

" Furthermore, the amino acids that

cradle the zinc atoms are completely conserved among

the three classes of

channels, telling us that during evolution there has

been selective pressure to

keep that zinc in place. "

All four kinds of Aplysia potassium channels studied

by Choe and colleagues

have analogs in the human nervous system, so the

investigators believe that

their studies of zinc's role in Aplysia channel

function are directly relevant to

understanding its function in the human brain.

First author of the study, titled " Zn2+-binding and

molecular determinants of

tetramerization in voltage-gated K+ channels, " is

Bixby, currently at

the University of California, San Diego. Other Salk

authors include s

Kreusch, a postdoctoral researcher in Choe's

laboratory and Max Nanao,

who is also a graduate student at the University of

California, San Diego. The

study was done in collaboration with N. Vivienne Shen

and J. Pffafinger

at Baylor College of Medicine and Henry Bellamy at

the Stanford Synchroton

Radiation Laboratory. The work was supported by the

National Institutes of

Health and the American Heart Association.

The Salk Institute for Biological Studies, located in

La Jolla, Calif., is an

independent nonprofit institution dedicated to

fundamental discoveries in the

life sciences, the improvement of human health and

conditions, and the training

of future generations of researchers. The Institute

was founded in 1960 by

Jonas Salk, M.D., with a gift of land from the City

of San Diego and the

financial support of the March of Dimes Birth Defects

Foundation.

RELATED

Stories

Newsgroups

Books

Sites

Copyright c 1995-98 ScienceDaily Magazine | Email:

editor@...

Best viewed with Internet Explorer or Netscape Navigator

(version 3.0 or