1fr0
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(New page: 200px<br /><applet load="1fr0" size="450" color="white" frame="true" align="right" spinBox="true" caption="1fr0" /> '''SOLUTION STRUCTURE OF THE HISTIDINE-CONTAINI...)
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Revision as of 13:03, 20 November 2007
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SOLUTION STRUCTURE OF THE HISTIDINE-CONTAINING PHOSPHOTRANSFER DOMAIN OF ANAEROBIC SENSOR KINASE ARCB FROM ESCHERICHIA COLI.
Overview
An Escherichia coli sensor kinase, ArcB, transfers a phosphoryl group to a, partner response regulator in response to anaerobic conditions., Multidimensional NMR techniques were applied to determine the solution, structure of the histidine-containing phosphotransfer signaling domain of, ArcB (HPt(ArcB)), which has a phosphorylation site, His717. The backbone, dynamics were also investigated by analyses of the (15)N relaxation data, and amide hydrogen exchange rates. Furthermore, the protonation states of, the histidine imidazole rings were characterized by means of (1)H and, (15)N chemical shifts at various pHs. The determined solution structure of, HPt(ArcB) contains five helices and forms a four-helix bundle motif like, other HPt domains. The obtained order parameters, S (2), [(1)H]-(15)N, heteronuclear NOE values, and chemical exchange parameters, R(ex), showed, that the alpha-helical regions of HPt(ArcB) are rigid on both picosecond, to nanosecond and microsecond to millisecond time scales. On the other, hand, helix D, which contains His717, exhibited low protection factors of, less than 4000, indicating the presence of fluctuations on a slower time, scale in helix D. These results suggest that HPt(ArcB) may undergo a small, conformational change in helix D upon phosphorylation. It was also shown, that the imidazole ring of His717 has a pK(a) value of 6.76, which is, similar to that of a solvent-exposed histidine imidazole ring, and that a, pair of deprotonated neutral tautomers are rapidly exchanged with each, other. This is consistent with the solution structure of HPt(ArcB), in, which the imidazole ring of His717 is exposed to the solvent.
About this Structure
1FR0 is a Single protein structure of sequence from Escherichia coli. Full crystallographic information is available from OCA.
Reference
Solution structure and dynamic character of the histidine-containing phosphotransfer domain of anaerobic sensor kinase ArcB from Escherichia coli., Ikegami T, Okada T, Ohki I, Hirayama J, Mizuno T, Shirakawa M, Biochemistry. 2001 Jan 16;40(2):375-86. PMID:11148031
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