Featured Research

from universities, journals, and other organizations

Sirtuin Protein Has A New Function; May Play Role In Lifespan Extension

Date:
January 7, 2003
Source:
Johns Hopkins Medical Institutions
Summary:
Scientists from Johns Hopkins and the University of Wisconsin have discovered that a protein called Sir2, which is found in nearly all living cells, has a new function that might help explain how calorie restriction can increase lifespans for some animals, the scientists say.

Scientists from Johns Hopkins and the University of Wisconsin have discovered that a protein called Sir2, which is found in nearly all living cells, has a new function that might help explain how calorie restriction can increase lifespans for some animals, the scientists say. Their report appeared in the Dec. 20 issue of Science.

A number of laboratories have shown that restricting total calorie intake extends the lifespans of organisms ranging from yeast to laboratory animals. Others have shown that this effect requires Sir2's protein family, called sirtuins, and increased cellular respiration, which is the process of using oxygen to convert calories into energy.

Studying bacteria, the Johns Hopkins-Wisconsin team has discovered that sirtuin controls the enzyme that converts acetate, a source of calories, into acetyl-CoA, a key component of cellular respiration.

"Sirtuins are highly conserved across species, but this is a never-before-described ability of the protein," says Jef Boeke, Ph.D., professor of molecular biology and genetics at Johns Hopkins' Institute for Basic Biomedical Sciences. "If sirtuins modify this enzyme in other organisms, turning on production of acetyl-CoA, it could help explain why restricting regular sources of calories -- sugars and fats -- leads to extended lifespan in many kinds of organisms."

Identified in all living creatures, including single-celled organisms like bacteria and yeast, sirtuin proteins previously were known to play an important role in keeping regions of chromosomes turned off. By modifying the histone proteins that keep DNA tightly coiled, sirtuins prevent certain regions of chromosomes from being exposed to cells' DNA-reading machinery.

Sirtuin's new role in bacteria involves the same modification as its interaction with histone -- removing an acetyl group, a "decoration" added to a protein's sequence (like phosphate) -- but the targeted protein is involved in producing energy, not controlling chromosomes.

Normally, cells can survive by using many different molecules as sources of energy -- potent sources like fats or sugars, or even relatively energy-poor molecules like acetate.

However, Jorge Escalante-Semerena and Vincent Starai of the University of Wisconsin created a strain of bacteria missing its sirtuin protein and noticed that it couldn't live on acetate. Boeke had previously noticed that yeast without sirtuin had the same problem, so the researchers dug deeper.

They discovered that the sirtuin protein in bacteria is a crucial modifier of an enzyme known as acetyl-CoA synthetase, which converts acetate into acetyl-CoA in a two-step process. Acetyl-CoA then can directly fuel the citric acid cycle, the central energy-producing step in cellular respiration.

"This is a completely new target for the sirtuin protein," says Boeke, who has been studying "transcriptional silencing" -- sirtuin's previously known role -- for some time. "Converting acetate isn't the cell's only way of making acetyl-CoA, but when acetate is the major energy source, it's crucial. Now we have to check for this role in other organisms."

The Wisconsin researchers found that sirtuin activates the first step of acetate's conversion, and Boeke and Johns Hopkins' Robert Cole and Ivana Celic figured out that sirtuin does so by removing an acetyl group from a lysine in the enzyme's active site.

While bacteria and yeast are both single-celled critters, yeast are much more closely related to animals, including humans, than are bacteria. If the yeast version of sirtuin also modifies the newly identified target, that would more likely reflect the protein's role in animals and would more formally link the protein to lifespan extension, at least for yeast. The effect of calorie restriction on the lifespan of bacteria has not been established.

###The studies were funded by the National Institutes of Health, and the Jerome Stefaniak and Pfizer Predoctoral Fellowships (to Starai). The Johns Hopkins Mass Spectrometry facility is funded by the National Center for Research Resources, the Johns Hopkins Fund for Medical Discovery, and the Johns Hopkins Institute for Cell Engineering. Authors on the paper are Starai and Escalante-Semerena of Wisconsin; and Celic, Cole and Boeke of the Johns Hopkins School of Medicine.


Story Source:

The above story is based on materials provided by Johns Hopkins Medical Institutions. Note: Materials may be edited for content and length.


Cite This Page:

Johns Hopkins Medical Institutions. "Sirtuin Protein Has A New Function; May Play Role In Lifespan Extension." ScienceDaily. ScienceDaily, 7 January 2003. <www.sciencedaily.com/releases/2003/01/030107072609.htm>.
Johns Hopkins Medical Institutions. (2003, January 7). Sirtuin Protein Has A New Function; May Play Role In Lifespan Extension. ScienceDaily. Retrieved October 21, 2014 from www.sciencedaily.com/releases/2003/01/030107072609.htm
Johns Hopkins Medical Institutions. "Sirtuin Protein Has A New Function; May Play Role In Lifespan Extension." ScienceDaily. www.sciencedaily.com/releases/2003/01/030107072609.htm (accessed October 21, 2014).

Share This



More Plants & Animals News

Tuesday, October 21, 2014

Featured Research

from universities, journals, and other organizations


Featured Videos

from AP, Reuters, AFP, and other news services

'Cadaver Dog' Sniffs out Human Remains

'Cadaver Dog' Sniffs out Human Remains

AP (Oct. 21, 2014) Where's a body buried? Buster's nose can often tell you. He's a cadaver dog, specially trained to find human remains and increasingly being used by law enforcement and accepted in courts. These dogs are helping solve even decades-old mysteries. (Oct. 21) Video provided by AP
Powered by NewsLook.com
White Lion Cubs Born in Belgrade Zoo

White Lion Cubs Born in Belgrade Zoo

AFP (Oct. 20, 2014) Two white lion cubs, an extremely rare subspecies of the African lion, were recently born at Belgrade Zoo. They are being bottle fed by zoo keepers after they were rejected by their mother after birth. Duration: 00:42 Video provided by AFP
Powered by NewsLook.com
Traditional Farming Methods Gaining Ground in Mali

Traditional Farming Methods Gaining Ground in Mali

AFP (Oct. 20, 2014) He is leading a one man agricultural revolution in Mali - Oumar Diatabe uses traditional farming methods to get the most out of his land and is teaching others across the country how to do the same. Duration: 01:44 Video provided by AFP
Powered by NewsLook.com
Goliath Spider Will Give You Nightmares

Goliath Spider Will Give You Nightmares

Buzz60 (Oct. 20, 2014) An entomologist stumbled upon a South American Goliath Birdeater. With a name like that, you know it's a terrifying creepy crawler. Sean Dowling (@SeanDowlingTV) has the details. Video provided by Buzz60
Powered by NewsLook.com

Search ScienceDaily

Number of stories in archives: 140,361

Find with keyword(s):
Enter a keyword or phrase to search ScienceDaily for related topics and research stories.

Save/Print:
Share:

Breaking News:

Strange & Offbeat Stories


Plants & Animals

Earth & Climate

Fossils & Ruins

In Other News

... from NewsDaily.com

Science News

Health News

Environment News

Technology News



Save/Print:
Share:

Free Subscriptions


Get the latest science news with ScienceDaily's free email newsletters, updated daily and weekly. Or view hourly updated newsfeeds in your RSS reader:

Get Social & Mobile


Keep up to date with the latest news from ScienceDaily via social networks and mobile apps:

Have Feedback?


Tell us what you think of ScienceDaily -- we welcome both positive and negative comments. Have any problems using the site? Questions?
Mobile: iPhone Android Web
Follow: Facebook Twitter Google+
Subscribe: RSS Feeds Email Newsletters
Latest Headlines Health & Medicine Mind & Brain Space & Time Matter & Energy Computers & Math Plants & Animals Earth & Climate Fossils & Ruins