Featured Research

from universities, journals, and other organizations

View Into The Human Body: The Formation Of Cell Organelles

Date:
February 21, 2009
Source:
Ruhr-Universitaet-Bochum
Summary:
Peroxisomes, multifaceted functional units within cells, fulfil the most diverse of tasks. In human beings, failure of these organelles is fatal. Their biogenesis does not adhere to the standard rules and still remains to be fully clarified. Scientists have identified a new pathway for components of the peroxisomal membrane proteins. The data gained is a significant contribution towards the comprehension of the formation and origin of peroxisomes.

Type 1 peroxisomal membrane proteins (PMPs) are synthesized on free ribosomes within the cytosol and bound to the peroxisomal membrane immediately after formation. By contrast, the Type 2 PMPs, which, according to the data gained in this study, include Pex3p and Pex22p, are initially transported to the endoplasmic reticulum and only subsequently to the peroxisomes.
Credit: Image courtesy of Ruhr-Universitaet-Bochum

Peroxisomes, multifaceted functional units within cells, fulfil the most diverse of tasks. In human beings, failure of these organelles is fatal. Their biogenesis does not adhere to the standard rules and still remains to be fully clarified.

Scientists from the research team under the auspices of Prof. Ralf Erdmann and Dr. Hanspeter Rottensteiner (Department of Systemic Biochemistry, Medical Faculty at the Ruhr University) have identified a new pathway for components of the peroxisomal membrane proteins.

The data gained is a significant contribution towards the comprehension of the formation and origin of peroxisomes.

Peroxisomes: Organelles with multifaceted functions

Peroxisomes are organelles responsible for a multitude of metabolic functions within cells. They contain over 50 different functional enzymes capable of forming highly variable structures adapted to the specific needs of the organism. One of the most important features of peroxisomes is the spatial isolation (compartmentalization) of metabolic pathways in which poisonous hydrogen peroxide is formed. Its destruction thereof is one of the most important functions of the peroxisomes.

Illnesses due to peroxisomal defects are usually fatal

Prof. Erdmann explained that the significance of these organelles is illustrated by the illnesses of patients suffering from defects in individual enzymes or a disorder in the biogenesis of the peroxisomes. Illnesses resulting from a biogenetic disorder are subsumed as the Zellweger spectrum and are usually so severe that the patients die during infancy. Clarification of the biogenesis of these organelles is essential for the development of approaches for diagnosis and treatment of these diseases.

Indirect formation of membranes

The research team at the RUB investigated – amongst other things – the origin and biogenesis of the peroxisomal membranes. Prof. Erdmann explained that the peroxisomal protein import machinery has to be assembled before the peroxisome can import the numerous enzymes required. The Pex3p protein is a decisive factor for importing membrane proteins, functioning as docking site on the membrane. These docking sites enable targeted insertion of newly formed proteins. To date, it has still not been fully clarified how Pex3p per se is integrated into the membrane. It could, however, be shown that newly formed Pex3p is initially incorporated in the cellular fluid of the endoplasmic reticulum (ER, another cell organelle). The subsequent mode of transport of Pex3p to the peroxisomes is still unknown. Prof. Erdmann stated that there is a significant difference between this pathway and that of other peroxisomal membrane proteins. The latter are incorporated directly into existent peroxisomes and require Pex3p for this procedure.

Assumed exclusive pathway transpired to be common

To date it has been assumed that Pex3p is the only peroxisomal protein that reaches the peroxisomes via the endoplasmic reticulum. The scientists at the RUB have now been able to prove that this is not the case. They compared the import pathways of Pex3p with those of Pex22p, another peroxisomal membrane protein, and were able to demonstrate that in each case a small fraction of these proteins already suffices to transport a fluorescent reporter protein to the peroxisomes. The segments of the protein that target a specific site are termed signal sequences.

The similarity between Pex3p and Pex22p signal sequences induced the scientists to exchange the two parts using molecular biological techniques and to subsequently investigate the functionality of the two thus altered proteins. Their analyses disclosed that the signal sequences of the two proteins are interchangeable without affecting their peroxisomal targeting. Further investigations showed that both proteins use the same pathway. This implies that this pathway is not exclusively used by Pex3p (as assumed to date) but rather constitutes a newly identified general pathway for peroxisomal membrane proteins. Moreover, this study showed that the Pex3p-signal sequence is responsible for targeting, but not - in contrast to the generally accepted opinion - for the specific function of Pex3p in the biogenesis of the peroxisomes.


Story Source:

The above story is based on materials provided by Ruhr-Universitaet-Bochum. Note: Materials may be edited for content and length.


Journal Reference:

  1. Halbach et al. The N-domain of Pex22p Can Functionally Replace the Pex3p N-domain in Targeting and Peroxisome Formation. Journal of Biological Chemistry, 2008; 284 (6): 3906 DOI: 10.1074/jbc.M806950200

Cite This Page:

Ruhr-Universitaet-Bochum. "View Into The Human Body: The Formation Of Cell Organelles." ScienceDaily. ScienceDaily, 21 February 2009. <www.sciencedaily.com/releases/2009/02/090210134548.htm>.
Ruhr-Universitaet-Bochum. (2009, February 21). View Into The Human Body: The Formation Of Cell Organelles. ScienceDaily. Retrieved July 25, 2014 from www.sciencedaily.com/releases/2009/02/090210134548.htm
Ruhr-Universitaet-Bochum. "View Into The Human Body: The Formation Of Cell Organelles." ScienceDaily. www.sciencedaily.com/releases/2009/02/090210134548.htm (accessed July 25, 2014).

Share This




More Plants & Animals News

Friday, July 25, 2014

Featured Research

from universities, journals, and other organizations


Featured Videos

from AP, Reuters, AFP, and other news services

Boy Attacked by Shark in Florida

Boy Attacked by Shark in Florida

Reuters - US Online Video (July 24, 2014) An 8-year-old boy is bitten in the leg by a shark while vacationing at a Florida beach. Linda So reports. Video provided by Reuters
Powered by NewsLook.com
Goma Cheese Brings Whiff of New Hope to DRC

Goma Cheese Brings Whiff of New Hope to DRC

Reuters - Business Video Online (July 24, 2014) The eastern region of the Democratic Republic of Congo, mainly known for conflict and instability, is an unlikely place for the production of fine cheese. But a farm in the village of Masisi, in North Kivu is slowly transforming perceptions of the area. Known simply as Goma cheese, the Congolese version of Dutch gouda has gained popularity through out the region. Ciara Sutton reports. Video provided by Reuters
Powered by NewsLook.com
Tyrannosaur Pack-Hunting Theory Aided By New Footprints

Tyrannosaur Pack-Hunting Theory Aided By New Footprints

Newsy (July 24, 2014) A new study claims a set of prehistoric T-Rex footprints supports the theory that the giant predators hunted in packs instead of alone. Video provided by Newsy
Powered by NewsLook.com
Bill Gates: Health, Agriculture Key to Africa's Development

Bill Gates: Health, Agriculture Key to Africa's Development

AFP (July 24, 2014) Health and agriculture development are key if African countries are to overcome poverty and grow, US software billionaire Bill Gates said Thursday, as he received an honourary degree in Ethiopia. Duration: 00:36 Video provided by AFP
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:
from the past week

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