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| | {{STRUCTURE_1t3i| PDB=1t3i | SCENE= }} | | {{STRUCTURE_1t3i| PDB=1t3i | SCENE= }} |
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| - | '''Structure of slr0077/SufS, the Essential Cysteine Desulfurase from Synechocystis PCC 6803'''
| + | ===Structure of slr0077/SufS, the Essential Cysteine Desulfurase from Synechocystis PCC 6803=== |
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| - | ==Overview==
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| - | Cysteine desulfurases, designated NifS, IscS, and SufS, cleave L-cysteine to form alanine and an enzyme cysteinyl persulfide intermediate. Genetic studies on the photosynthetic cyanobacterium Synechocystis sp. PCC 6803 have shown that of the three Nif/Isc/SufS-like proteins encoded in its genome only the sequence group II protein, Slr0077/SufS, is essential. This protein has been overexpressed in Escherichia coli, purified to homogeneity, shown to bind pyridoxal-5'-phosphate (PLP) and to catalyze cysteine desulfuration, and characterized in terms of its structure and kinetics. The results suggest that catalysis in the absence of accessory factors has two constituent pathways, one involving nucleophilic attack by C372 to form the Slr0077/SufS-bound cysteinyl persulfide intermediate and the second involving intermolecular attack by the sulfur of a second molecule of the substrate on the initial l-cysteine-PLP complex to form free l-cysteine persulfide. The second pathway is operant in the C372A variant protein, explaining why it retains significant activity, which is proportional to the concentration of l-cysteine (i.e., does not saturate). C-S bond cleavage by the first (normal) pathway is considerably less efficient than the equivalent step in a group I desulfurase (Slr0387) from the same organism (characterized in the accompanying paper). The 1.8 A crystal structure of the protein, which is very similar to that previously reported for E. coli SufS, shows that the loop on which C372 resides is well-ordered and shorter by 11 residues than the corresponding disordered loop of the group I NifS-like protein from Thermotoga maritima. Sequence comparisons establish that the T. maritima and Slr0387 proteins have loops of similar length. The combined structural and kinetic data imply that the modest activity of Slr0077/SufS and other SufS proteins in comparison to their sequence group I (NifS/IscS-like) paralogues results from inefficiency in the nucleophilic attack step associated with differences in the structure or dynamics of this loop. The recent reports that SufS proteins can be activated manyfold by binding to SufE thus implies that the accessory protein either accelerates nucleophilic attack by the conserved cysteine residue of SufS by a conformational mechanism or itself contributes a nucleophilic cysteine for more efficient intermolecular attack.
| + | The line below this paragraph, {{ABSTRACT_PUBMED_15379559}}, adds the Publication Abstract to the page |
| | + | (as it appears on PubMed at http://www.pubmed.gov), where 15379559 is the PubMed ID number. |
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| | + | {{ABSTRACT_PUBMED_15379559}} |
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| | ==About this Structure== | | ==About this Structure== |
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| | [[Category: Cysteine desulfurase]] | | [[Category: Cysteine desulfurase]] |
| | [[Category: Plp-binding enzyme]] | | [[Category: Plp-binding enzyme]] |
| - | ''Page seeded by [http://oca.weizmann.ac.il/oca OCA ] on Sat May 3 09:28:23 2008'' | + | |
| | + | ''Page seeded by [http://oca.weizmann.ac.il/oca OCA ] on Mon Jul 28 16:17:39 2008'' |
Revision as of 13:17, 28 July 2008
Template:STRUCTURE 1t3i
Structure of slr0077/SufS, the Essential Cysteine Desulfurase from Synechocystis PCC 6803
Template:ABSTRACT PUBMED 15379559
About this Structure
1T3I is a Single protein structure of sequence from Synechocystis sp.. Full crystallographic information is available from OCA.
Reference
Kinetic and structural characterization of Slr0077/SufS, the essential cysteine desulfurase from Synechocystis sp. PCC 6803., Tirupati B, Vey JL, Drennan CL, Bollinger JM Jr, Biochemistry. 2004 Sep 28;43(38):12210-9. PMID:15379559
Page seeded by OCA on Mon Jul 28 16:17:39 2008
