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 SBC Current Beamline Statistics

SBC
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19

2013
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Total
ID
BM
ID
BM
ID
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PDB Deposits:
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49
227
28
20
5
4423
81
16
68
14
14
5
1554
 

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STUDY REVEALS HOW EBOLA BLOCKS IMMUNE SYSTEM

 

APS/APCF Symposium & MCSG 14th Annual Meeting The symposium reviewed the achievements of X-ray macromolecular crystallography and the future structural biology opportunities in biomedical and biological sciences. We assessed the progress on understanding structures of proteins and their families and will contemplate the future impact of new free electron laser light sources on biology and chemistry. The potential contribution and impact of Advanced Photon Source upgrade and new protein research facilities were discussed in the context of future advances in structural and molecular biology. Thank you to those who attended. 

Newly ID'd protein provides tArget for antibiotic-resistant hospital bacterium

 

STRUCTURAL BIOLOGY REVEALS THE SECRETS OF DISEASES

 

 

 

 

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Crystal structures of alkylperoxo and anhydride intermediates in an intradiol ring-cleaving dioxygenase.

Knoot CJ, Purpero VM, Lipscomb JD. Proc Natl Acad Sci U S A. 2015 Jan 13;112(2):388-93.

Proposed intermediates in the reaction of 3,4-PCD with substrate and O2. R represents either COOH (PCA) or F (4FC). 4FC is bound in the equatorial plane rather than the axial plane as shown in 2. It may rotate to the axial plane to react. The πop-sym highest occupied molecular orbital of substrate is proposed to be the source of the reducing equivalents (15).

 

Intradiol aromatic ring-cleaving dioxygenases use an active site, nonheme Fe(3+) to activate O2 and catecholic substrates for reaction. The inability of Fe(3+) to directly bind O2 presents a mechanistic conundrum. The reaction mechanism of protocatechuate 3,4-dioxygenase is investigated here using the alternative substrate 4-fluorocatechol. This substrate is found to slow the reaction at several steps throughout the mechanistic cycle, allowing the intermediates to be detected in solution studies. When the reaction was initiated in an enzyme crystal, it was found to halt at one of two intermediates depending on the pH of the surrounding solution. The X-ray crystal structure of the intermediate at pH 6.5 revealed the key alkylperoxo-Fe(3+) species, and the anhydride-Fe(3+) intermediate was found for a crystal reacted at pH 8.5. Intermediates of these types have not been structurally characterized for intradiol dioxygenases, and they validate four decades of spectroscopic, kinetic, and computational studies. In contrast to our similar in crystallo crystallographic studies of an Fe(2+)-containing extradiol dioxygenase, no evidence for a superoxo or peroxo intermediate preceding the alkylperoxo was found. This observation and the lack of spectroscopic evidence for an Fe(2+) intermediate that could bind O2 are consistent with concerted formation of the alkylperoxo followed by Criegee rearrangement to yield the anhydride and ultimately ring-opened product. Structural comparison of the alkylperoxo intermediates from the intra- and extradiol dioxygenases provides a rationale for site specificity of ring cleavage.

PDB: 4WHO

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