Cyanobacteria class II fructose-1,6-bisphoshate aldolase (Cy-FBA-II) and cyanobacteria fructose-1,6-bisphosphatase (Cy-FBPase) are two neighboring key regulatory enzymes in the Calvin cycle of the cyanobacteria photosynthesis system. Each of them might be taken as a potential target for designing novel inhibitors to chemically control harmful algal blooms (HABs). In the present paper, a series of novel inhibitors were rationally designed, synthesized, and optimized based upon the structural and interactional information of both Cy-FBA-II and Cy-FBPase, and their inhibitory activities were examined in vitro and in vivo. The experimental results showed that compounds L19e-L19g exhibited moderate inhibitory activities (IC50 = 28.1-103.2 ?M) against both Cy-FBA-II and Cy-FBPase; compounds L19a-L19d, L19h, L20a-L20d exhibited high Cy-FBA-II inhibitory activities (IC50 = 2.3-16.9 ?M) and moderate Cy-FBPase inhibitory activities (IC50 = 31.5-141.2 ?M); however, compounds L20e-L20h could potently inhibit both Cy-FBA-II and Cy-FBPase with IC50 values less than 30 ?M, which demonstrated more or less dual-target inhibitors feature. Moreover, most of them exhibited potent algicide activity (EC50 = 0.8-22.3 ppm) against cyanobacteria Synechocystis sp. PCC 6803.
In the present study, the electronic energy transfer pathways in trimeric and hexameric aggregation state of cyanobacteria C-phycocyanin (C-PC) were investigated in term of the Förster theory. The corresponding excited states and transition dipole moments of phycocyanobilins (PCBs) located into C-PC were examined by model chemistry in gas phase at time-dependent density functional theory (TDDFT), configuration interaction-singles (CIS), and Zerners intermediate neglect of differential overlap (ZINDO) levels, respectively. Then, the long-range pigment-protein interactions were approximately taken into account by using polarizable continuum model (PCM) at TDDFT level to estimate the influence of protein environment on the preceding calculated physical quantities. The influence of the short-range interaction caused by aspartate residue nearby PCBs was examined as well. Only when the protonation of PCBs and its long- and short-range interactions were properly taken into account, the calculated energy transfer rates (1/K) in the framework of Förster model at TDDFT/B3LYP/6-31+G* level were in good agreement with the experimental results of C-PC monomer and trimer. Furthermore, the present calculated results suggested that the energy transfer pathway in C-PC monomer is predominant from ?-155 to ?-84 (1/K = 13.4 ps), however, from ?-84 of one monomer to ?-84 (1/K = 0.3-0.4 ps) in a neighbor monomer in C-PC trimer. In C-PC hexamer, an additional energy flow was predicted to be from ?-155 (or ?-84) in top trimer to adjacent ?-155 (or ?-84) (1/K = 0.5-2.7 ps) in bottom trimer.
3-Hydroxy-3-methylglutaryl coenzyme A reductase (HMGR) is a primary target in the current clinical treatment of hypercholesterolemia with specific inhibitors of "statin" family. Statins are excellent inhibitors of the class I (human) enzyme but relatively poor inhibitors of the class II enzyme, which are well-known as a potential target to discover drugs fighting against the invasive diseases originated from S. pneumoniae . However, no significantly effective inhibitors of class II HMGR have been reported so far. In the present study, the reasonable three-dimensional (3D) structure of class II HMGR from S. pneumoniae (SP-HMGR-II) was built by Swissmodel. On the basis of the modeling 3D structure in "close" flap domain form, several novel potential hit compounds out of SPECs database were picked out by using structure-based screening strategy. Especially the compounds 4, 3, and 11 exhibit highly inhibitory activities, with IC50 values of 11.5, 18.5, and 18.1 ?M, respectively. Furthermore, the hit compounds were chosen as probe molecules, and their probable interactions with the corresponding individual residues have been examined by jointly using the molecular docking, site-directed mutagenesis, enzymatic assays, and fluorescence spectra, to provide an insight into a new special binding-model located between the HMG-CoA and NADPH pockets. The good agreement between theoretical and experimental results indicate that the modeling strategies and screening processes in the present study are very likely to be a promising way to search novel lead compounds with both structural diversity and high inhibitory activity against SP-HMGR-II in the future.
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