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| | {{STRUCTURE_1s4v| PDB=1s4v | SCENE= }} | | {{STRUCTURE_1s4v| PDB=1s4v | SCENE= }} |
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| - | '''The 2.0 A crystal structure of the KDEL-tailed cysteine endopeptidase functioning in programmed cell death of Ricinus communis endosperm'''
| + | ===The 2.0 A crystal structure of the KDEL-tailed cysteine endopeptidase functioning in programmed cell death of Ricinus communis endosperm=== |
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| - | ==Overview==
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| - | In the senescing endosperm of germinating castor bean (Ricinus communis) a special organelle (the ricinosome) releases a papain-type cysteine endopeptidase (CysEP) during the final stages of cellular disintegration. Protein cleavage sites for the Ricinus CysEP were determined with fluorogenic peptides (Abz-Xaa-Arg-/-Gln-Gln-Tyr(NO2)-Asp). The highest kcat/Km values were obtained with neutral amino acid residues with large aliphatic and non-polar (Leu, Val, Ile, Met) or aromatic (Phe, Tyr, Trp) side-chains. A second series (Abz-Leu-Xaa-/Gln-Pro-Tyr(NO2)-Asp) was evaluated. Based on these results, the covalent binding inhibitor H-D-Val-Leu-Lys-chloromethylketone (CMK) was chosen as substrate analogue for replacement in the catalytic site. Unusually, CysEP cleaved beta-casein N and C-terminal to the amino acid proline. CysEP was crystallized, its structure was solved by molecular replacement at 2.0 A resolution and refined to a R-factor of 18.1% (Rfree=22.6%). The polypeptide chain folds as in papain into two domains divided by the active site cleft, an elongated surface depression harboring the active site. The non-primed specificity subsites of the proteinase are clearly defined by the H-D-Val-Leu-Lys-CMK-inhibitor covalently bound to the active site. The absence of the occluding loop, which blocks the active site of exopeptidases at the C-terminal side of the scissile bond, identifies CysEP as an endopeptidase. The more open pocket of the Ricinus CysEP correlates with the extended variety of substrate amino acid residues accommodated by this enzyme, including even proline at the P1 and P1' positions. This may allow the enzyme to attack a greater variety of proteins during programmed cell death.
| + | The line below this paragraph, {{ABSTRACT_PUBMED_15037072}}, adds the Publication Abstract to the page |
| | + | (as it appears on PubMed at http://www.pubmed.gov), where 15037072 is the PubMed ID number. |
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| | + | {{ABSTRACT_PUBMED_15037072}} |
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| | ==About this Structure== | | ==About this Structure== |
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| | [[Category: Seed germination]] | | [[Category: Seed germination]] |
| | [[Category: Senescence]] | | [[Category: Senescence]] |
| - | ''Page seeded by [http://oca.weizmann.ac.il/oca OCA ] on Sat May 3 08:18:00 2008'' | + | |
| | + | ''Page seeded by [http://oca.weizmann.ac.il/oca OCA ] on Mon Jul 28 10:08:00 2008'' |
Revision as of 07:08, 28 July 2008
Template:STRUCTURE 1s4v
The 2.0 A crystal structure of the KDEL-tailed cysteine endopeptidase functioning in programmed cell death of Ricinus communis endosperm
Template:ABSTRACT PUBMED 15037072
About this Structure
1S4V is a Single protein structure of sequence from Ricinus communis. Full crystallographic information is available from OCA.
Reference
The 2.0 A crystal structure and substrate specificity of the KDEL-tailed cysteine endopeptidase functioning in programmed cell death of Ricinus communis endosperm., Than ME, Helm M, Simpson DJ, Lottspeich F, Huber R, Gietl C, J Mol Biol. 2004 Mar 5;336(5):1103-16. PMID:15037072
Page seeded by OCA on Mon Jul 28 10:08:00 2008
