The effect of Hg++ was studied on the arrangement and photoactivity of NADPH:protochlorophyllide oxidoreductase (POR) in homogenates of dark-grown wheat (Triticum aestivum L.) leaves. 77 K fluorescence emission spectra of the homogenates were recorded before and after the irradiation of the homogenates and the spectra were deconvoluted into Gaussian components. The mercury treatment caused a precipitation of the membrane particles, which was followed by a remarkable decrease of the fluorescence yield. 10-3 M Hg++ decreased the ratio of the 655 nm-emitting protochlorophyllide (Pchlide) form to the 633 nm-emitting form. 10-2 M Hg++ shifted the short wavelength band to 629-630 nm and a 655 nm form was observed which was inactive on irradiation. This inhibition may be caused by serious alteration of the enzyme structure resulting in the trans-localisation of NADPH within the active site of POR. and K. Lenti, F. Fodor, B. Böddi.
Nitrogen is an essential factor for normal plant and algal development. As a component of nucleic acids, proteins, and chlorophyll (Chl) molecules, it has a crucial role in the organization of a functioning photosynthetic apparatus. Our aim was to study the effects of nitrogen starvation in cultures of the unicellular green alga, Chlamydomonas reinhardtii, maintained on nitrogen-free, and then on nitrogen-containing medium. During the three-week-long degreening process, considerable changes were observed in the Chl content, the ratio of Chl-protein complexes, and photosynthetic activity of the cultures as well as in the ultrastructure of single chloroplasts. The regreening process was much faster then the degradation; total greening of the cells occurred within four days. The rate of regeneration depended on the nitrogen content. At least 50% of the normal nitrogen content of Tris-Acetate-Phosphate (TAP) medium was required in the medium for the complete regreening of the cells and regeneration of chloroplasts., É. Preininger, A. Kósa, Z. S. Lőrincz, P. Nyitrai, J. Simon, B. Böddi, Á. Keresztes, I. Gyurján., and Obsahuje seznam literatury
Prolamellar bodies (PLBs) isolated from dark-grown, 6.5-d-old leaves of wheat (Triticum aesíivum L. cv. Kosack) were treated with the carboxylic acid cross-linker l-ethyl-3-[3-(diniethylaniino)propyl]carbodiimide (EDC) or with the lysině specific cross-linker 2-iniinothiolane. SDS-PAGE showed that the most prominenent cross- linked product was a dimer of the NADPH-protochlorophyllide oxidoreductase (PCR), but also larger aggregates of the polypeptide were identified by inununological detection on electro-blots. A two-dimensional diagonál gel showed that much of the cross-linking was between the PCR polypeptides. The cross-linkers induced a shift of the fluorescence peak to shorter wavelengths, a bandwidth increase of the fluorescence peak, and an increase of the fluorescence yield. In the presence of NADPH the blue shift was reduced, but the increase in the fluorescence yield still occmred. A cross-linker treatment of PLBs prior to solubilization with 1-0-n-octyl-P -D-glucopyranoside (octylglucoside) delayed, but did not prevent the spectral shifts from 657 to 646 nm and from 646 to 635 nm observed in non-cross-linked detergent- treated PLBs. The cross-linking did not prevent a spectral shift, corresponding to the Shibata shift, of Chlide. Thus the spectral shifts are not strictly coupled to disaggregation of the PCR polypeptides.