Phytochrome proteins

Figure 4. White light microscope images of cells transfected with GFP (A) show GFP fluorescence when observed with a fluorescent microscope (C) but with no fluorescence at the longer wavelength where phytochrome fluorescence is observed. White light microscope images (B) of cells that express both GFP and phytochrome proteins show equivalent images of GFP fluorescence (D) and phytochrome fluorescence (F).

Antibody, scFv, against phytochrome Suspension Nicotiana tabacum (tobacco) A. tumefaciens transformation of leaf explant CaMV 35S Tobacco pathogenesis related protein (PRla) 0.5 mg L-1 (e) 5.0% of total medium protein (e) 73... 

Kay It is external coincidence. Both are required. If you activate phytochrome A (phjA) and cryptochrome 2 cry 2) in wild-type plants at the end of the day in short days this has no effect on flowering because the phase of CO expression is such that it is at too low a level. It really seems to be entrainment regulating CO waveform. This is where Bunning in the 1940s was brilliant in proposing how this could work. This story will get even prettier when we fulfil the prediction that this light is leading to some post-translational modulation of CO protein or potentially a CO partner. 

Phytochrome is found not only in higher plants but also in algae, where it controls the movement of chloroplasts,611 and also in cyanobacteria.623 54 Cyano-bacterial phytochromes contain histidine kinase domains, which may function in a two-component system with a response regulator similar to protein CheY of the chemotaxis system in E. coli (Fig. 19-5).624/625 Some nonphotosynthetic bacteria also use bacteriophytochromes for light sensing. In some cases biliverdin (Fig. 24-24) is the chromophore.6253... 

Figure 11. Corrected stationary UV (protein) fluorescence spectra of 124-kDa P, phytochrome and of the red-light adapted mixture Pr + Pfr at 275 K A c = 295 nm (Holzwarth et al. [108]).

TABLE 2 Lifetimes and Approximate Maxima of Time-Resolved UV (Protein) Fluorescence Spectra of 124-kDa Pr Phytochrome from Oat and of the Red-Light Adapted Pr + Pfr Mixture at 275 K [78, 108 ... 

Figure 13. Time-resolved decay-associated spectra of the UV (protein) fluorescence components i, rp)i - 4 of Pr phytochrome (124 kDa) and of the red-light adapted Pr + Pfr mixture obtained by global analysis. The dashed line corresponds to the stationary fluorescence spectrum obtained by A c = 295 nm (cf. Figure 11). The amplitudes of the two sets of spectra can be compared on an absolute basis (Holzwarth et al. [108]).

Addition of 20-25% (v/v) ethylene glycol, known to stabilize native protein structures, has often been found to be a convenient measure also for phytochrome. Absorption spectroscopy showed that the additive does not cause any loss of Pr fcf Pfr photochromicity, and the lifetimes and amplitudes of the Pj components [108] as well as the kinetic parameters of the absorption decays of 1 qq and I200 [113] at 272-297 K (Table 3) were hardly affected either. This is in accord with a confinement of the sequence Pr - I700 - Ibi t0 the phytochromobilin-binding protein domain without... 

A search for other agents to modify the dynamics of the Pr -> Pfr transformation, and in particular to influence differentially the reaction intermediates, focused on cellular constituents which presumably interact in vivo with phytochrome. Ubiquitin, an 8.5-kDa protein claimed to bind covalently in vivo to Pfr [160] has now also been found to interact in vitro with Pr in the absence of any other cellular constituent [161]. The protein... 

These conclusions are still consistent with the finding that significant conformational differences between Pr and Pfr do in fact exist ([65,147] for reviews see [8c, 148]). They can be rationalized—albeit not with conclusive rigour—by a conformational adaptation of the apoprotein part located around the bilatriene-binding pocket, following the Z E photoisomerization of the chromophore. This local change then should suffice to determine through bilatriene chromophore-protein interactions the spectroscopic characteristics of the chromophore as well as stability and reactivity of the two photochromic forms of phytochrome. 

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