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Peptidyl-prolyl cis-trans Isomerases in the Chloroplast Thylakoid Lumen
Linköpings universitet, Institutionen för klinisk och experimentell medicin, Cellbiologi. Linköpings universitet, Hälsouniversitetet.
2007 (Engelska)Doktorsavhandling, sammanläggning (Övrigt vetenskapligt)
Abstract [en]

The Sun is the ultimate energy source on Earth. Photosynthetic organisms are able to catalyze the conversion of solar energy to chemical energy by a reaction called photosynthesis. In plants, this process occurs inside a green organelle called the chloroplast. The protein complexes involved in the photosynthetic light reactions are situated in the thylakoid membrane, which encloses a tiny space called lumen. The Peptidyl-Prolyl cis-trans Isomerase (PPIase) family is the most abundant protein family in the thylakoid lumen. The three PPIase subfamilies, cyclophilins, FKBPs (FK506 binding proteins) and parvulins form a group by their enzymatic activity despite lack of sequence similarity between the subfamilies. Cyclophilins and FKBPs, collectively called immunophilins, were originally discovered as the targets of the immunosuppressive drugs cyclosporine A and FK506, respectively. By suppressing the immune response in humans, these immunophilin-drug complexes revolutionized the field of organ transplantation by preventing graft rejection. Cis-trans isomerization of peptide bonds preceding the amino acid proline is the rate-limiting step of protein folding and several immunophilins have been shown to be important for catalysis of protein folding in vivo. PPIases have been found to be part of large protein complexes as well as in functions such as signalling, protein secretion, RNA processing and cell cycle control. A picture is therefore emerging in which the actual interaction between the PPIase and its target is perhaps more important than the PPIase activity.

In the present work, PPIases have been characterized in the chloroplast thylakoid lumen of Spinacia oleracea (spinach) and Arabidopsis thaliana (Arabidopsis). The most active PPIase in the spinach lumen was identified as the cyclophilin TLP20. AtCYP20-2, the Arabidopsis homologue of TLP20, was found to be upregulated at high light and attached to the thylakoid membrane, more precisely to the outer regions of photosystem II supercomplexes. In Arabidopsis, up to 5 cyclophilins and 11 FKBPs were predicted to reside in the lumen. Of these 16 immunophilins, only 2 were identified as active PPIases and significant differences were observed between the two plant species. AtCYP20-2, like TLP20, is an active isomerase although AtFKBP13 is the most active PPIase in the lumen of Arabidopsis. Mutant Arabidopsis plants deficient in AtCYP20-2 displayed no phenothypical changes or decrease in total lumenal PPIase activity. Being the only active PPIase in the mutants, the redox sensitive AtFKBP13 is proposed to compensate for the lack of AtCYP20-2 by oxidative activation. In agreement with the experimental data, the sequence analyses of catalytic domains of lumenal immunophilins demonstrate that only AtCYP20-2 and AtFKBP13 possess the amino acids found essential for PPIase activity in earlier studies of human cyclophilin A and FKBP12. It is concluded that with the exception of AtCYP20-2 and AtFKBP13 most immunophilins in the lumen of Arabidopsis lost their PPIase activity on peptide substrates and developed other specialized functions.

Ort, förlag, år, upplaga, sidor
Institutionen för biomedicin och kirurgi , 2007.
Serie
Linköping University Medical Dissertations, ISSN 0345-0082 ; 983
Nyckelord [en]
Peptidyl-prolyl isomerase activity, Cyclophilin, FKBP, Immunophilin, Chloroplast Thylakoid Lumen, protein characterization
Nationell ämneskategori
Cell- och molekylärbiologi
Identifikatorer
URN: urn:nbn:se:liu:diva-8531ISBN: 978-91-85715-76-3 (tryckt)OAI: oai:DiVA.org:liu-8531DiVA, id: diva2:23310
Disputation
2007-03-09, Berzeliussalen, Hälsouniversitetet, Linköpings Universitet, Linköping, 09:30 (Engelska)
Opponent
Handledare
Tillgänglig från: 2007-04-10 Skapad: 2007-04-10 Senast uppdaterad: 2020-03-29
Delarbeten
1. The major peptidyl-prolyl isomerase activity in thylakoid lumen of plant chloroplasts belongs to a novel cyclophilin TLP20
Öppna denna publikation i ny flik eller fönster >>The major peptidyl-prolyl isomerase activity in thylakoid lumen of plant chloroplasts belongs to a novel cyclophilin TLP20
2003 (Engelska)Ingår i: FEBS Letters, ISSN 0014-5793, Vol. 542, nr 1-3, s. 137-141Artikel i tidskrift (Refereegranskat) Published
Abstract [en]

Fractionation of proteins from the thylakoid lumen of spinach chloroplasts combined with peptidyl-prolyl cis/trans isomerase (PPIase) measurements revealed a major isomerase activity that was ascribed to a novel enzyme TLP20 ( hylakoid umen PIase of kDa). TLP20 was inhibited by cyclosporin A and mass spectrometric sequencing of tryptic peptides confirmed its classification as a cyclophilin. Genes encoding similar putative thylakoid cyclophilins with a unique insert of three amino acids NPV in their N-termini were found in chromosome 5 of both Arabidopsis and rice. TLP20 is suggested to be the major PPIase and protein folding catalyst in the thylakoid lumen of plant chloroplasts.

Nyckelord
Cyclophilin, Mass spectrometry, Peptidyl-prolyl isomerase activity, Spinach, Thylakoid lumen
Nationell ämneskategori
Medicin och hälsovetenskap
Identifikatorer
urn:nbn:se:liu:diva-14355 (URN)10.1016/S0014-5793(03)00366-1 (DOI)
Tillgänglig från: 2007-04-10 Skapad: 2007-04-10 Senast uppdaterad: 2009-05-08
2. Arabidopsis AtCYP20-2 is a light-regulated cyclophilin-type peptidyl-prolyl cis-trans isomerase associated with the photosynthetic membranes
Öppna denna publikation i ny flik eller fönster >>Arabidopsis AtCYP20-2 is a light-regulated cyclophilin-type peptidyl-prolyl cis-trans isomerase associated with the photosynthetic membranes
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2004 (Engelska)Ingår i: Plant Physiology, ISSN 0032-0889, Vol. 134, nr 4, s. 1244-1247Artikel i tidskrift (Refereegranskat) Published
Nationell ämneskategori
Medicin och hälsovetenskap
Identifikatorer
urn:nbn:se:liu:diva-14356 (URN)10.1104/pp.104.041186 (DOI)
Tillgänglig från: 2007-04-10 Skapad: 2007-04-10 Senast uppdaterad: 2009-05-29
3. Profound redox sensitivity of peptidyl-prolyl isomerase activity in Arabidopsis thylakoid lumen
Öppna denna publikation i ny flik eller fönster >>Profound redox sensitivity of peptidyl-prolyl isomerase activity in Arabidopsis thylakoid lumen
2006 (Engelska)Ingår i: FEBS Letters, ISSN 0014-5793, Vol. 580, nr 15, s. 3671-3676Artikel i tidskrift (Refereegranskat) Published
Abstract [en]

Proteomic, enzymatic, and mutant analyses revealed that peptidyl-prolyl isomerase (PPIase) activity in the chloroplast thylakoid lumen of Arabidopsis is determined by two immunophilins: AtCYP20-2 and AtFKBP13. These two enzymes are responsible for PPIase activity in both soluble and membrane-associated fractions of thylakoid lumen suggesting that other lumenal immunophilins are not active towards the peptide substrates. In thiol-reducing conditions PPIase activity of the isolated AtFKBP13 and of the total thylakoid lumen is suppressed several fold. Profound redox-dependence of PPIase activity implies oxidative activation of protein folding catalysis under oxidative stress and photosynthetic oxygen production in the thylakoid lumen of plant chloroplasts.

Nyckelord
Immunophilin; FKBP; Cyclophilin; Peptidyl-prolyl isomerase; Thylakoid lumen; Arabidopsis thaliana
Nationell ämneskategori
Medicin och hälsovetenskap
Identifikatorer
urn:nbn:se:liu:diva-14357 (URN)10.1016/j.febslet.2006.05.054 (DOI)
Tillgänglig från: 2007-04-10 Skapad: 2007-04-10 Senast uppdaterad: 2009-06-04
4. Knockout of AtCYP20-2 confirms degeneration of peptidyl-prolyl isomerase activity of immunophilins in the thylakoid lumen of Arabidopsis thaliana
Öppna denna publikation i ny flik eller fönster >>Knockout of AtCYP20-2 confirms degeneration of peptidyl-prolyl isomerase activity of immunophilins in the thylakoid lumen of Arabidopsis thaliana
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2007 (Engelska)Artikel i tidskrift (Refereegranskat) Submitted
Nationell ämneskategori
Medicin och hälsovetenskap
Identifikatorer
urn:nbn:se:liu:diva-14358 (URN)
Tillgänglig från: 2007-04-10 Skapad: 2007-04-10

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