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Enzymatic metal-chelation by porphyrins

Hansson, Andreas LU (2002)
Abstract (Swedish)
Popular Abstract in Swedish

Vad har jag gjort de senaste åren? Och varför? Det är det många som har undrat. Så stundtals även jag. Vad jag skriver nedan syftar inte till att förklara detta, utan är bara ämnat som en kort introduktion.



Jag har de senaste åren jobbat med gener och proteiner från både växter och bakterier. Både gener och proteiner är väldigt små saker, men även den minsta lilla sak kan vara av stor betydelse ibland. Just de gener och proteiner som jag har studerat är involverade i att tillverka ännu mindre saker. Trots sin otroligt ringa storlek syns dessa små små saker väldigt bra. Växter är till exempel alldeles fulla av en utav dessa små saker och blir därav alldeles gröna. Detta kallas... (More)
Popular Abstract in Swedish

Vad har jag gjort de senaste åren? Och varför? Det är det många som har undrat. Så stundtals även jag. Vad jag skriver nedan syftar inte till att förklara detta, utan är bara ämnat som en kort introduktion.



Jag har de senaste åren jobbat med gener och proteiner från både växter och bakterier. Både gener och proteiner är väldigt små saker, men även den minsta lilla sak kan vara av stor betydelse ibland. Just de gener och proteiner som jag har studerat är involverade i att tillverka ännu mindre saker. Trots sin otroligt ringa storlek syns dessa små små saker väldigt bra. Växter är till exempel alldeles fulla av en utav dessa små saker och blir därav alldeles gröna. Detta kallas klorofyll. Inom oss bär vi omkring på miljarder av den andra lilla saken som tillverkas av de protiner jag studerat. Av den lilla saken blir vårt blod alldeles rött. Denna kallas heme. Trots att dessa två små saker är fundamentalt olika både till färg och förekomst har de förvillande likheter. De är faktiskt så lika att man kan undra hur de kan bli tillverkade utan att de blandas ihop. Det är en fråga som jag har funderat på ibland.



För att kunna besvara denna typ utav frågor har jag bland annat muterat olika gener. Detta i förhoppning att dessa mutationer skall leda till att proteinerna blir alldeles till sig och jag då kan lura något nytt ur dem. Tyvärr lyckas inte detta alltid. Om det däremot skulle lyckas, då blir man glad och skriver ner sina resultat i en vetenskqplig tidskrift, i hopp om att andra skall finna det läsvärt.



Förstår ni? (Less)
Abstract
This thesis deals with the structure and function of two different enzymes, ferrochelatase and magnesium chelatase, that catalyse similar reactions. When this work started, a three-dimensional model of ferrochelatase existed. Much was known about the enzyme, but some details remained unclear. The focus has been to establish where the metal and the porphyrin binds to the enzyme, and how they are put together into one. From experiments performed, binding sites for the two substrates were established. It was found that ferrochelatase binds the porphyrin in a vice like grip and induces a distortion of the ring (paper II). The metal ion has been shown to bind close to the porphyrin (paper V). These findings taken together can provide a model... (More)
This thesis deals with the structure and function of two different enzymes, ferrochelatase and magnesium chelatase, that catalyse similar reactions. When this work started, a three-dimensional model of ferrochelatase existed. Much was known about the enzyme, but some details remained unclear. The focus has been to establish where the metal and the porphyrin binds to the enzyme, and how they are put together into one. From experiments performed, binding sites for the two substrates were established. It was found that ferrochelatase binds the porphyrin in a vice like grip and induces a distortion of the ring (paper II). The metal ion has been shown to bind close to the porphyrin (paper V). These findings taken together can provide a model for the catalytic mechanism of the enzyme (paper II and V).



Magnesium chelatase, that consists of three different subunits, was a more open field. With access to a collection of barley mutants, deficient in chlorophyll biosynthesis, some questions regarding magnesium chelatase were intended to be answered. Three barley mutants, that each segregated in three distinguished phenotypes served as a starting point. These mutants were found to be deficient in the smallest subunit (paper I). To further characterise the mutants and how subunits interact, the corresponding mutations were introduced in a bacterial magnesium chelatase (paper IV). A big leap forward came with the three-dimensional structure of the smallest subunit (paper III)



While the data presented in this thesis is converging future research on ferrochelatase to fewer questions, it has done quite the opposite for magnesium chelatase. Thanks to what is presented here, it is now known that the smallest magnesium chelatase subunit belongs to the AAA+ class of ATPases (paper III). Further it has been suggested that the middle sized subunit shows similarities to integrins (paper III), a group of cell surface receptors. The connection between AAA+ proteins and integrins was not previously mentioned, but later similar arrangements have been found in other proteins. However the mechanism of magnesium chelatase is still unknown. Hopefully the new aspects presented here will contribute to reveal its secrets. (Less)
Please use this url to cite or link to this publication:
author
opponent
  • Prof O'Brian, Mark, State University of New York at Buffalo, Department of Biochemistry, Buffalo, NY, U.S.A.
organization
publishing date
type
Thesis
publication status
published
subject
keywords
tetrapyrrole, Plant biochemistry, Växtbiokemi, MIDAS, metallation, magnesium chelatase, integrin, heme, ferrochelatase, chlorophyll, barley, AAA+, ATPase
pages
116 pages
publisher
Mats Hansson, Department of Biochemistry, Centre for Chemistry and Chemical Engineering, Lund University E-mail Mats.Hansson@biokem.lu.se,
defense location
Lecture Hall A, Chemical Centre
defense date
2002-12-13 13:15
ISBN
91-628-5473-9
language
English
LU publication?
yes
id
dd705edc-0976-41e8-bc4f-3c611c5a9b7e (old id 465245)
date added to LUP
2007-10-14 15:17:36
date last changed
2016-09-19 08:45:11
@phdthesis{dd705edc-0976-41e8-bc4f-3c611c5a9b7e,
  abstract     = {This thesis deals with the structure and function of two different enzymes, ferrochelatase and magnesium chelatase, that catalyse similar reactions. When this work started, a three-dimensional model of ferrochelatase existed. Much was known about the enzyme, but some details remained unclear. The focus has been to establish where the metal and the porphyrin binds to the enzyme, and how they are put together into one. From experiments performed, binding sites for the two substrates were established. It was found that ferrochelatase binds the porphyrin in a vice like grip and induces a distortion of the ring (paper II). The metal ion has been shown to bind close to the porphyrin (paper V). These findings taken together can provide a model for the catalytic mechanism of the enzyme (paper II and V).<br/><br>
<br/><br>
Magnesium chelatase, that consists of three different subunits, was a more open field. With access to a collection of barley mutants, deficient in chlorophyll biosynthesis, some questions regarding magnesium chelatase were intended to be answered. Three barley mutants, that each segregated in three distinguished phenotypes served as a starting point. These mutants were found to be deficient in the smallest subunit (paper I). To further characterise the mutants and how subunits interact, the corresponding mutations were introduced in a bacterial magnesium chelatase (paper IV). A big leap forward came with the three-dimensional structure of the smallest subunit (paper III)<br/><br>
<br/><br>
While the data presented in this thesis is converging future research on ferrochelatase to fewer questions, it has done quite the opposite for magnesium chelatase. Thanks to what is presented here, it is now known that the smallest magnesium chelatase subunit belongs to the AAA+ class of ATPases (paper III). Further it has been suggested that the middle sized subunit shows similarities to integrins (paper III), a group of cell surface receptors. The connection between AAA+ proteins and integrins was not previously mentioned, but later similar arrangements have been found in other proteins. However the mechanism of magnesium chelatase is still unknown. Hopefully the new aspects presented here will contribute to reveal its secrets.},
  author       = {Hansson, Andreas},
  isbn         = {91-628-5473-9},
  keyword      = {tetrapyrrole,Plant biochemistry,Växtbiokemi,MIDAS,metallation,magnesium chelatase,integrin,heme,ferrochelatase,chlorophyll,barley,AAA+,ATPase},
  language     = {eng},
  pages        = {116},
  publisher    = {Mats Hansson, Department of Biochemistry, Centre for Chemistry and Chemical Engineering, Lund University E-mail Mats.Hansson@biokem.lu.se,},
  school       = {Lund University},
  title        = {Enzymatic metal-chelation by porphyrins},
  year         = {2002},
}