Review of Studies on the Last Enzymes in Bacteriochlorophyll (Bchl) and Chlorophyll (Chl) Biosynthesis

This paper summarizes the information available online related to mechanisms of Chlorophyll and Bacteriochlorophyll biosynthesis, emphasizing four enzymes in its last steps. The biosynthesis of Chlorophyll (Chl)/Bacteriochlorophyll (Bchl) is essential for the occurrence of photosynthesis. Four enzymes catalyze parts of the last chemical reactions steps to biosynthesize Bchl/Chl;they are: The Light-Dependent Protochlorophyllide (Pchlide) Oxidoreductase (LPOR: EC 1.3.1.33), the Light-Independent Pchlide oxidoreductase (DPOR: EC 1.3.7.7), Chlide Reductase (COR: EC 1.3.99.35) and the Divinyl Reductase (DVR: EC 1.3.1.75). These enzymes catalyze the reductions reactions of tetrapyrrole’s rings in the Chlorophyll and Bacteriochlorophyll biosynthesis process. This review has the aim to organize, analyze and compare the most important discoveries related to these four enzymes discovered so far. The comparisons are made with the information from the bibliography used, and the sequence of these enzymes got from online database. Sequence alignment, phylogenetic and molecular evolutionary analysis of all the four enzymes was conducted to find their levels of similarities.

Effect of Photo-Oxidation on Energy Transfer in Light Harvesting Complex （LH2） from Rhodobacter Sphaeroides 601

We study the photo-oxidation of bacteriochlorophylls （BChls） in peripheral light harvesting complexes （LH2） from rhodobacter sphaeroides by using the steady absorption and the femtosecond pump-probe measurement, to realize the detailed dynamics of LH2 in the presence of photo-oxidation. The experimental results reveal that BChl-B850 radical cations may act as an additional channel to compete with the unoxidized BChl-B850 molecules for rapidly releasing the excitation energy, while the B800→B850 energy transfer rate is almost unaffected in the oxidation process.

Component spectroscopic properties of light-harvesting complexes with DFT calculations

Photosynthesis is a fundamental process in biosciences and biotechnology that influences profoundly the research in other disciplines.In this paper,we focus on the characterization of fundamental components,present in pigment-protein complexes,in terms of their spectroscopic properties such as infrared spectra,nuclear magnetic resonance,as well as nuclear quadrupole resonance,which are of critical importance for many applications.Such components include chlorophylls and bacteriochlorophylls.Based on the density functional theory method,we calculate the main spectroscopic characteristics of these components for the Fenna-Matthews-Olson light-harvesting complex,analyze them and compare them with available experimental results.Future outlook is discussed in the context of current and potential applications of the presented results.

Structural insights into the unusual core photocomplex from a triply extremophilic purple bacterium,Halorhodospira halochloris

Halorhodospira(Hlr.)halochloris is a triply extremophilic phototrophic purple sulfur bacterium,as it is thermophilic,alkaliphilic,and extremely halophilic.The light-harvesting-reaction center(LH1–RC)core complex of this bacterium displays an LH1-Q_(y)transition at 1,016 nm,which is the lowest-energy wavelength absorption among all known phototrophs.Here we report the cryo-EM structure of the LH1–RC at 2.42?resolution.The LH1 complex forms a tricyclic ring structure composed of 16αβγ-polypeptides and oneαβ-heterodimer around the RC.From the cryo-EM density map,two previously unrecognized integral membrane proteins,referred to as protein G and protein Q,were identified.Both of these proteins are single transmembrane-spanning helices located between the LH1 ring and the RC Lsubunit and are absent from the LH1–RC complexes of all other purple bacteria of which the structures have been determined so far.Besides bacteriochlorophyll b molecules(B1020)located on the periplasmic side of the Hlr.halochloris membrane,there are also two arrays of bacteriochlorophyll b molecules(B800 and B820)located on the cytoplasmic side.Only a single copy of a carotenoid(lycopene)was resolved in the Hlr.halochloris LH1–α3β3 and this was positioned within the complex.The potential quinone channel should be the space between the LH1–α3β3 that accommodates the single lycopene but does not contain aγ-polypeptide,B800 and B820.Our results provide a structural explanation for the unusual Q_(y)red shift and carotenoid absorption in the Hlr.halochloris spectrum and reveal new insights into photosynthetic mechanisms employed by a species that thrives under the harshest conditions of any phototrophic microorganism known.

Characterization of ＇Pinky＇ Strain Grown in Culture of Rhodobacter sphaeroides R26.1

In the process of cultivating Rhodobater sphaeroides R26.1, some of which turned from blue to pink due to the irradiation of a beam of leaking white light. The mutant strains were named ＇pinky＇ strains, which were cultivated in the red light and in the dark for a comparative study. It turned out that the strains did not grow in the dark, so they might be photosynthetic bacteria. The electronic absorption spectrum of the ＇pinky＇ strains was measured, which shows they contained two main photosynthetic pigments, carotenoids（Cars） and bacteriochlorophylls（BChls）. And then they were extracted and analyzed. It proves that Bchls included Bchl a and Bchl a＇. Nuclear magnetic resonance （NMR） spectra were exploited to determine the chemical structure of Cars. The results indicate that there were seven kinds of Cars, including lycopene, rhodopin, anhydrorhodovibrin, 3,4-dihydroanhydrorhodovibrin, 3,3,4- dihydrospirilloxanthin, 3,4,3＇,4＇-tetrahydrospirilloxanthin and spirilloxanthin. Based on the above results, it was found that most identified Cars formed via spirilloxanthin biosynthesis pathway. The analyzed results of 16S rRNA gene show that the homology of ＇pinky＇ strains with Rhodopseudomonas palusteris was 99%. Rhodopseudomonas palusteris has been cultivated in our laboratory. Because of its strong vitality, it did not become extinct with so many years passing. When Rhodobater sphaeroides R26.1 was cultivated, it got rejuvenated under the appropriate conditions and caused Rhodobater sphaeroides R26.1 to be contaminated.