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PSI Scientific Report 2008

Research focus and highlights – Synchrotron light  23

Figure 2: Close view of the central funnel of native ASST showing a sulfuryl group in the active site. A full understanding of the active site was only possible after combining multiple crystallographic and biochemical experiments.

electrospray ionization mass spectrometery was performed

trometry, combined with multiple crystallographic models

on both the native and sulfurylated forms of the enzyme.

enabled us to understand the architecture of the active site

Together with the crystal structure of native ASST, results from

and thus elucidate the catalytic pathway of the enzyme.

these experiments clearly demonstrated that His-436 is the

The complete account of the work described here can be found

residue that undergoes transient covalent sulfurylation during

in reference [1].

catalysis. Structural analysis of the two intermediate forms of ASST showed, for the first time, this high-energy sulfurylhistidine intermediate state, confirming the proposed ping-

References

pong reaction pathway.

[1] G. Malojc˘ic´, R. L. Owen, J. P. A. Grimshaw, M. S. Brozzo,

The experiments summarised here provide a basis for under-

H. Dreher-Teo and R. Glockshuber, PNAS, 105

standing sulfuryl transfer in a manner independent of the

19217–19222 (2008).

universal sulfuryl donor (adenosine 3’-phosphate-5’-phos-

[2] J. P. A. Grimshaw et al., J Mol Biol, 380 667–680 (2008).

phosulfate, PAPS) in mammals, opening up medically interest-

[3] R. L. Owen et al., J Synchrotron Rad, 16 173–182 (2009).

ing perspectives. ASST is a promising target for antibacterial drugs, and together the crystal structures and biochemical data provide a basis for drug design targeting this virulence factor. It is also interesting to note that these insights were only made possible by combining crystallographic, spectroscopic [3], and other biochemical methods. An advanced form of mass spec-

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Scientific Report 2008  

The whole range of PSI's research in more than 100 pages – this is what the new Scientific Report has to offer. Examples of the latest scien...

Scientific Report 2008  

The whole range of PSI's research in more than 100 pages – this is what the new Scientific Report has to offer. Examples of the latest scien...