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Substrate-binding model of the chlorophyll biosynthetic magnesium chelatase BchH subunit.

Sirijovski, Nickolche; Lundqvist, Joakim LU ; Rosenbäck, Matilda; Elmlund, Hans LU ; Al-Karadaghi, Salam LU ; Willows, Robert D and Hansson, Mats LU (2008) In Journal of Biological Chemistry 283(17). p.11652-11660
Abstract
Photosynthetic organisms require chlorophyll and bacteriochlorophyll to harness light energy and transform water and carbon dioxide into carbohydrates and oxygen. The biosynthesis of these pigments is initiated by magnesium chelatase, an enzyme composed of BchI, BchD and BchH proteins, which catalyzes the insertion of Mg(2+) into protoporphyrin IX (Proto) to produce Mg-protoporphyrin IX. BchI and BchD form an ATP dependant AAA(+) complex that transiently interacts with the Proto-binding BchH subunit, at which point Mg(2+) is chelated. In this study, controlled proteolysis, electron microscopy of negatively stained specimens and single-particle 3D reconstruction have been used to probe the structure and substrate binding mechanism of the... (More)
Photosynthetic organisms require chlorophyll and bacteriochlorophyll to harness light energy and transform water and carbon dioxide into carbohydrates and oxygen. The biosynthesis of these pigments is initiated by magnesium chelatase, an enzyme composed of BchI, BchD and BchH proteins, which catalyzes the insertion of Mg(2+) into protoporphyrin IX (Proto) to produce Mg-protoporphyrin IX. BchI and BchD form an ATP dependant AAA(+) complex that transiently interacts with the Proto-binding BchH subunit, at which point Mg(2+) is chelated. In this study, controlled proteolysis, electron microscopy of negatively stained specimens and single-particle 3D reconstruction have been used to probe the structure and substrate binding mechanism of the BchH subunit to a resolution of 25 A. The apo structure contains three major lobe-shaped domains connected at a single point, with additional densities at the tip of two lobes termed the thumb and finger. With the independent reconstruction of a substrate bound BchH complex (BchH-Proto) we observed a distinct conformational change in the thumb and finger subdomains. Prolonged proteolysis of native apo BchH produced a stable C-terminal fragment of 45 kDa, and Proto was shown to protect the full polypeptide from degradation. Fitting of a truncated BchH polypeptide reconstruction identified the N- and C-terminal domains. Our results show that the N- and C-terminal domains play crucial roles in the substrate-binding mechanism. (Less)
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author
organization
publishing date
type
Contribution to journal
publication status
published
subject
in
Journal of Biological Chemistry
volume
283
issue
17
pages
11652 - 11660
publisher
ASBMB
external identifiers
  • pmid:18263581
  • wos:000255067400066
  • scopus:45549091468
ISSN
1083-351X
DOI
10.1074/jbc.M709172200
language
English
LU publication?
yes
id
e7ed5463-161c-4b7d-9b64-f4d320b79e3b (old id 1042097)
date added to LUP
2008-03-25 16:25:18
date last changed
2017-07-30 03:41:26
@article{e7ed5463-161c-4b7d-9b64-f4d320b79e3b,
  abstract     = {Photosynthetic organisms require chlorophyll and bacteriochlorophyll to harness light energy and transform water and carbon dioxide into carbohydrates and oxygen. The biosynthesis of these pigments is initiated by magnesium chelatase, an enzyme composed of BchI, BchD and BchH proteins, which catalyzes the insertion of Mg(2+) into protoporphyrin IX (Proto) to produce Mg-protoporphyrin IX. BchI and BchD form an ATP dependant AAA(+) complex that transiently interacts with the Proto-binding BchH subunit, at which point Mg(2+) is chelated. In this study, controlled proteolysis, electron microscopy of negatively stained specimens and single-particle 3D reconstruction have been used to probe the structure and substrate binding mechanism of the BchH subunit to a resolution of 25 A. The apo structure contains three major lobe-shaped domains connected at a single point, with additional densities at the tip of two lobes termed the thumb and finger. With the independent reconstruction of a substrate bound BchH complex (BchH-Proto) we observed a distinct conformational change in the thumb and finger subdomains. Prolonged proteolysis of native apo BchH produced a stable C-terminal fragment of 45 kDa, and Proto was shown to protect the full polypeptide from degradation. Fitting of a truncated BchH polypeptide reconstruction identified the N- and C-terminal domains. Our results show that the N- and C-terminal domains play crucial roles in the substrate-binding mechanism.},
  author       = {Sirijovski, Nickolche and Lundqvist, Joakim and Rosenbäck, Matilda and Elmlund, Hans and Al-Karadaghi, Salam and Willows, Robert D and Hansson, Mats},
  issn         = {1083-351X},
  language     = {eng},
  number       = {17},
  pages        = {11652--11660},
  publisher    = {ASBMB},
  series       = {Journal of Biological Chemistry},
  title        = {Substrate-binding model of the chlorophyll biosynthetic magnesium chelatase BchH subunit.},
  url          = {http://dx.doi.org/10.1074/jbc.M709172200},
  volume       = {283},
  year         = {2008},
}