Journal:Angew Chem Int Ed:1

We constructed, purified, and solved the crystal structure of water soluble chlorophyll binding protein from cauliflower complex with chlorophyll ''a'' (CaWSCP-Chl ''a''). <scene name='72/727875/Cv/4'>CaWSCP tetramer</scene>. Chains A, B, C, and D are coloured <font color='purple'><b>purple</b></font>, <span style="color:pink;background-color:black;font-weight:bold;">pink</span>, <span style="color:slategrey;background-color:black;font-weight:bold;">grey</span>, and <font color='blue'><b>blue</b></font>. Chlorophylls are shown in ball-and-stick representation with <span style="color:cyan;background-color:black;font-weight:bold;">carbons in cyan colour</span>. The structure is highly homologous to the previously elucidated structure of native WSCP from ''Lepidium virginicum'' (LvWSCP; PDB ID: [[2dre]]). Overall, the structure of recombinant CaWSCP and <scene name='72/727875/Cv/9'>that of native LvWSCP are very similar</scene>. <span style="color:brown;background-color:black;font-weight:bold;">LvWSCP shown in brown</span> with <span style="color:orange;background-color:black;font-weight:bold;">Chl carbons in orange</span>. Both assemble as symmetric homotetramers in which each monomeric subunit binds a single Chl. This results in an <scene name='72/727875/Cv/10'>arrangement of four Chls that is in fact a dimer of excitonically coupled Chl dimers</scene>. Overall, the protein structures and Chl arrangements of the <scene name='72/727875/Cv/11'>monomeric</scene> and <scene name='72/727875/Cv/6'>dimeric</scene> subunits of LvWSCP and CaWSCP are highly homologous. But, the interfaces between the <scene name='72/727875/Cv/8'>dimeric subunits in the tetramer and hence the relative orientation of Chl dimers are not the same</scene>. Aligning the dimeric subunits of CaWSCP and LvWSCP reveals about 60º <scene name='72/727875/Cv/18'>difference in rotation of one dimeric subunit around the C2 symmetry axes</scene> of the adjacent dimer. <scene name='72/727875/Cv/17'>Click here to see animation of this scene</scene>. <span style="color:deeppink;background-color:black;font-weight:bold;">Dimers AB of CaWSCP and LvWSCP both colored in deeppink</span>, <span style="color:yellow;background-color:black;font-weight:bold;">dimer CD of CaWSCP is in yellow</span> and <span style="color:salmon;background-color:black;font-weight:bold;">dimer CD of LvWSCP is in salmon</span>. A view from chains A and B toward chains C and D of CaWSCP and LvWSCP revealing the <scene name='72/727875/Cv/21'>rotation of the LvWSCP Chl dimer with respect to the CaWSCP Chl dimer</scene>. For clarity, protein chains, and Chl phytyl chains are not presented. <scene name='72/727875/Cv/22'>Opposite view</scene> from chain C and D toward chains A an B.

We constructed, purified, and solved the crystal structure of water soluble chlorophyll binding protein from cauliflower complex with chlorophyll ''a'' (CaWSCP-Chl ''a''). <scene name='72/727875/Cv/4'>CaWSCP tetramer</scene>. Chains A, B, C, and D are coloured <font color='purple'><b>purple</b></font>, <span style="color:pink;background-color:black;font-weight:bold;">pink</span>, <span style="color:slategrey;background-color:black;font-weight:bold;">grey</span>, and <font color='blue'><b>blue</b></font>. Chlorophylls are shown in ball-and-stick representation with <span style="color:cyan;background-color:black;font-weight:bold;">carbons in cyan colour</span>. The structure is highly homologous to the previously elucidated structure of native WSCP from ''Lepidium virginicum'' (LvWSCP; PDB ID: [[2dre]]). Overall, the structure of recombinant CaWSCP and <scene name='72/727875/Cv/9'>that of native LvWSCP are very similar</scene>. <span style="color:brown;background-color:black;font-weight:bold;">LvWSCP shown in brown</span> with <span style="color:orange;background-color:black;font-weight:bold;">Chl carbons in orange</span>. Both assemble as symmetric homotetramers in which each monomeric subunit binds a single Chl. This results in an <scene name='72/727875/Cv/10'>arrangement of four Chls that is in fact a dimer of excitonically coupled Chl dimers</scene>. Overall, the protein structures and Chl arrangements of the <scene name='72/727875/Cv/11'>monomeric</scene> and <scene name='72/727875/Cv/6'>dimeric</scene> subunits of LvWSCP and CaWSCP are highly homologous. But, the interfaces between the <scene name='72/727875/Cv/8'>dimeric subunits in the tetramer and hence the relative orientation of Chl dimers are not the same</scene>. Aligning the dimeric subunits of CaWSCP and LvWSCP reveals about 60º <scene name='72/727875/Cv/18'>difference in rotation of one dimeric subunit around the C2 symmetry axes</scene> of the adjacent dimer. <scene name='72/727875/Cv/17'>Click here to see animation of this scene</scene>. <span style="color:deeppink;background-color:black;font-weight:bold;">Dimers AB of CaWSCP and LvWSCP both colored in deeppink</span>, <span style="color:yellow;background-color:black;font-weight:bold;">dimer CD of CaWSCP is in yellow</span> and <span style="color:salmon;background-color:black;font-weight:bold;">dimer CD of LvWSCP is in salmon</span>. A view from chains A and B toward chains C and D of CaWSCP and LvWSCP revealing the <scene name='72/727875/Cv/21'>rotation of the LvWSCP Chl dimer with respect to the CaWSCP Chl dimer</scene>. For clarity, protein chains, and Chl phytyl chains are not presented. <scene name='72/727875/Cv/22'>Opposite view</scene> from chain C and D toward chains A an B.

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