RuBisCO: Difference between revisions

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{{STRUCTURE_1rcx|  PDB=1rcx  | SIZE=400| SCENE= |right|CAPTION=Spinach RuBisCO 8 large and 8 small chains complex with substrate ribulose-1,5- bisphosphate, [[1rcx]] }}
{{STRUCTURE_1rcx|  PDB=1rcx  | SIZE=400| SCENE= |right|CAPTION=Spinach RuBisCO 8 large and 8 small chains complex with substrate ribulose-1,5- bisphosphate, [[1rcx]] }}


'''Ribulose-1,5-bisphosphate carboxylase oxygenase – RuBisCO''' (RBCO) catalyzes the first step in photosynthetic carbon fixation, and it is the most abundant protein on earth.  RBCO can either carboxylate or oxygenate ribulose-1,5-bisphosphate (RUBP) with CO<sub>2</sub> or O<sub>2</sub>, respectively.  RBCO from flowering plants  consists of eight large subunits and eight  small subunits.  2-carboxylarabinitol-1,5-bisphosphate (2-CABP) is an inhibitor of RCBO.  Some additional details can be found in [[Ribulose-1,5-bisphosphate carboxylase/oxygenase]].
'''Ribulose-1,5-bisphosphate carboxylase oxygenase – RuBisCO''' (RBCO) catalyzes the first step in photosynthetic carbon fixation, and it is the most abundant protein on earth.  RBCO can either carboxylate or oxygenate ribulose-1,5-bisphosphate (RUBP) with CO<sub>2</sub> or O<sub>2</sub>, respectively.  RBCO from flowering plants  consists of eight large subunits and eight  small subunits.  Some additional details can be found in [[Ribulose-1,5-bisphosphate carboxylase/oxygenase]].


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== Large Subunit Structure ==
== Large Subunit Structure ==
(under construction)


Here is an isolated <scene name='46/463261/Rubisco_lsu_pair/7'>pair of large subunits</scene>. Each subunit has a large C-terminal lobe and a small N-terminal lobe, and the subunits are arranged head-to-toe (antiparallel) in the pair. <scene name='46/463261/Rubisco_lsu_pair/5'>Two active sites</scene> are located in the interface of the large subunit pair. The subunits are shown in cartoon with one shown in the secondary structure color scheme. Each active site is occupied by RUBP, which is shown in CPK spacefill. Here is a <scene name='46/463261/Rubisco_lsu_monomer/1'>single large subunit</scene> showing that both lobes contain alpha helices (pink) and beta strands (yellow). The large lobe is dominated by an <scene name='46/463261/Rubisco_lsu_monomer/2'>α-β barrel</scene> (amino acids 166-409), which contributes most of the residues that form the the active site. One residue from the N-terminal lobe of the adjacent large subunit <scene name='46/463261/Asn123/1'>Asn 123</scene> completes the active site. This scene shows RUBP in spacefill and CPK in one of the active sites in the dimer. Both subunits are shown in transparent cartoon with the α-β barrel is pink and yellow. Asn 123 from the adjacent subunit is in blue spacefill, and residues 121-129 are shown in blue cartoon. This residue does not contribute to catalysis, and it will not be considered further.
Here is an isolated <scene name='46/463261/Rubisco_lsu_pair/7'>pair of large subunits</scene>. Each subunit has a large C-terminal lobe and a small N-terminal lobe, and the subunits are arranged head-to-toe (antiparallel) in the pair. <scene name='46/463261/Rubisco_lsu_pair/5'>Two active sites</scene> are located in the interface of the large subunit pair. The subunits are shown in cartoon with one shown in the secondary structure color scheme. Each active site is occupied by RUBP, which is shown in CPK spacefill. Here is a <scene name='46/463261/Rubisco_lsu_monomer/1'>single large subunit</scene> showing that both lobes contain alpha helices (pink) and beta strands (yellow). The large lobe is dominated by an <scene name='46/463261/Rubisco_lsu_monomer/2'>α-β barrel</scene> (amino acids 166-409), which contributes most of the residues that form the the active site. One residue from the N-terminal lobe of the adjacent large subunit <scene name='46/463261/Asn123/1'>Asn 123</scene> completes the active site. This scene shows RUBP in spacefill and CPK in one of the active sites in the dimer. Both subunits are shown in transparent cartoon with the α-β barrel is pink and yellow. Asn 123 from the adjacent subunit is in blue spacefill, and residues 121-129 are shown in blue cartoon. This residue does not contribute to catalysis, and it will not be considered further.
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(under construction)
(under construction)


The active site is formed by an α-β barrel, which comprises the C-terminal lobe of the large subunit. Some additional residues are contributed by the N-terminal lobe of the adjacent subunit.  Here is an <scene name='46/463261/Rubisco_lsu_pair/5'>isolated pair of subunits</scene>, , and here is the α-β barrel of that subunit.  
This scene shows an <scene name='46/463261/8ruc_active-site/1'>isolated α-β barrel</scene> (cartoon and colored for secondary structure) of spinach Rubisco [[8ruc]], bound to the naturally occurring inhibitor 2-carboxylarabinitol-1,5-bisphosphate (2-CABP) and Mg<sup>2+</sup>, both shown in CPK spacefill. 2-CABP sits at one end of the α-β barrel, only residues from the beta strands and loops that link them to helices contribute to the active site.  




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