IngentaConnect On the Configurational and Conformational Changes in Photoactive ...

Abstract:

Photoactive Yellow Protein (PYP), a phototaxis photoreceptor from Ectothiorhodospira halophila, is a small water-soluble protein that is crystallisable and excellently photo-stable. It can be activated with light ( lgr ^max = 446 nm), to enter a series of transient intermediates that jointly form the photocycle of this photosensor protein. The most stable of these transient states is the signalling state for phototaxis, pB. The spatial structure of the ground state of PYP, pG and the spectral properties of the photocycle intermediates have been very well resolved. Owing to its excellent chemical- and photochemical stability, also the spatial structure of its photocycle intermediates has been characterised with X-ray diffraction and multinuclear NMR spectroscopy. Surprisingly, the results obtained showed that their structure is dependent on the molecular context in which they are formed. Therefore, a large range of diffraction-, scattering- and spectroscopic techniques is now being employed to resolve in detail the dynamical changes of the structure of PYP while it progresses through its photocycle. This approach has led to considerable progress, although some techniques still result in mutually inconsistent conclusions regarding aspects of the structure of particular intermediates. Recently, significant progress has also been made with simulations with molecular dynamics analyses of the initial events that occur in PYP upon photo activation. The great challenge in this field is to eventually obtain agreement between predicted dynamical alterations in PYP structure, as obtained with the MD approach and the actually measured dynamical changes in its structure as evolving during photocycle progression.

Keywords: 4-hydroxy-cinnamic acid; contact dependence; hysteresis; photoactive yellow protein; photo-isomerisation; polarization spectroscopy; protein dynamics; time-resolved X-ray diffraction; time-resolved FTIR spectroscopy; transient intermediates

Language: English

Document Type: Research article

Affiliations: 1: Laboratory for Microbiology, Swammerdam Institute for Lifesciences, BioCentrum Amsterdam and University of Amsterdam

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On the Configurational and Conformational Changes in Photoactive Yellow Protein that Leads to Signal Generation in Ectothiorhodospira halophila