1s4v
From Proteopedia
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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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[[Category: Simpson, D J.]] | [[Category: Simpson, D J.]] | ||
[[Category: Than, M E.]] | [[Category: Than, M E.]] | ||
| - | [[Category: | + | [[Category: Endosperm]] |
| - | [[Category: | + | [[Category: Kdel er retention signal]] |
| - | [[Category: | + | [[Category: Ricinosome]] |
| - | [[Category: | + | [[Category: Seed germination]] |
| - | [[Category: | + | [[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 | + | |
Revision as of 05:18, 3 May 2008
The 2.0 A crystal structure of the KDEL-tailed cysteine endopeptidase functioning in programmed cell death of Ricinus communis endosperm
Overview
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.
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 Sat May 3 08:18:00 2008
