1ugu
From Proteopedia
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Crystal structure of PYP E46Q mutant
Overview
Photoactive yellow protein from Ectothiorhodospira halophila is a, photoreceptor protein involved in the negative phototaxis of this, bacterium. Its chromophore (p-coumaric acid) is deprotonated in the ground, state, which is stabilized by a hydrogen-bond network between Tyr42, Glu46, and Thr50. Glu46 is a key residue as it has been suggested that the proton, at Glu46 is transferred to the chromophore during its photoconversion from, the dark state to the signalling state. The structure of E46Q mutant, protein was determined at 1.2 A resolution, revealing that the phenolic O, atom of p-coumaric acid is hydrogen bonded to NH(2) of Gln46 in E46Q with, a longer distance (2.86 +/- 0.02 A) than its distance (2.51 A) to Glu46 OH, in the wild type. This and the decreased thermal stability of E46Q, relative to the wild type show that this hydrogen bond is weakened in the, E46Q mutant compared with the corresponding bond in the wild type. Several, characteristic features of E46Q such as an alkali shift in the pK(a) and, the rapid photocycle can be explained by this weakened hydrogen bond., Furthermore, the red shift in the absorption maximum in E46Q can be, explained by the delocalization of the electron on the phenolic oxygen of, p-coumaric acid owing to the weakening of this hydrogen bond.
About this Structure
1UGU is a Single protein structure of sequence from Halorhodospira halophila with HC4 as ligand. Full crystallographic information is available from OCA.
Reference
Structure of photoactive yellow protein (PYP) E46Q mutant at 1.2 A resolution suggests how Glu46 controls the spectroscopic and kinetic characteristics of PYP., Sugishima M, Tanimoto N, Soda K, Hamada N, Tokunaga F, Fukuyama K, Acta Crystallogr D Biol Crystallogr. 2004 Dec;60(Pt 12 Pt 2):2305-9. Epub, 2004 Nov 26. PMID:15583378
Page seeded by OCA on Wed Nov 21 04:06:46 2007
