CP29, one of the minor light-harvesting complexes of higher-plant photosystem II, absorbs and transfers solar energy for photosynthesis and also has important roles in photoprotection. We have solved the crystal structure of spinach CP29 at 2.80-Å resolution. Each CP29 monomer contains 13 chlorophyll and 3 carotenoid molecules, which differs considerably from the major light-harvesting complex LHCII and the previously proposed CP29 model. The 13 chlorophyll-binding sites are assigned as eight chlorophyll a sites, four chlorophyll b and one putative mixed site occupied by both chlorophylls a and b. Based on the present X-ray structure, an integrated pigment network in CP29 is constructed. Two special clusters of pigment molecules, namely a615-a611-a612-Lut and Vio(Zea)-a603-a609, have been identified and might function as potential energy-quenching centers and as the exit or entrance in energy-transfer pathways.

Tauopathies are neurodegenerative diseases characterized by intracellular amyloid deposits of tau protein. Missense mutations in the tau gene ( MAPT ) correlate with aggregation propensity and cause dominantly inherited tauopathies, but their biophysical mechanism driving amyloid formation is poorly understood. Many disease-associated mutations localize within tau’s repeat domain at inter-repeat interfaces proximal to amyloidogenic sequences, such as 306 VQIVYK 311 . We use cross-linking mass spectrometry, recombinant protein and synthetic peptide systems, in silico modeling, and cell models to conclude that the aggregation-prone 306 VQIVYK 311 motif forms metastable compact structures with its upstream sequence that modulates aggregation propensity. We report that disease-associated mutations, isomerization of a critical proline, or alternative splicing are all sufficient to destabilize this local structure and trigger spontaneous aggregation. These findings provide a biophysical framework to explain the basis of early conformational changes that may underlie genetic and sporadic tau pathogenesis.

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This study was conducted to determine the effects of dietary probiotic supplementation on the ileal digestibilities of nutrients and growth performance in broilers. Two thousand, eight hundred and eighty male broiler chickens at 1 day of age were randomly allotted to eight treatment groups and fed for 6 weeks the maize-soybean meal-based diets containing 0, 0.2, 0.4 or 0.6% AgiPro A100 (a probiotic) and 0 or 6 ppm flavomycin (an antibiotic). This well-established antibiotic was used as a positive control for the efficacy of AgiPro A100. Dietary supplementation with either the probiotic or the antibiotic alone did not affect (P > 0.05) feed intake or average daily gain (ADG) of broilers between days 1 and 42 of life. However, there was a significant antibiotic × probiotic interaction effect (P < 0.05) in increasing ADG during the entire experimental period. Notably, dietary supplementation with the probiotic or the antibiotic consistently improved (P < 0.05) the ileal digestibilities of crude protein and most amino acids in 21-and 42-day-old chickens. Supplementing the probiotic to broiler diets also improved (P < 0.05) the ileal digestibilities of dry matter, energy, calcium and phosphate in the birds. Collectively, these results indicated that AgiPro A100 is an effective alternative to flavomycin in chicken production.

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Pathogenesis of tauopathies involves conversion of tau monomer into pathological tau conformers that serve as templates to recruit native tau into growing assemblies. Small soluble tau seeds have been proposed to drive pathological tau assembly in vitro, in cells and in vivo. We have previously described the isolation of monomeric pathogenic tau seeds derived from recombinant samples and tauopathy tissues but in-depth biophysical characterization of these species has not been done. Here we describe a chromatographic method to isolate recombinant soluble tau seeds derived from heparin treatment. We used biochemical and biophysical approaches to show that the seeds are predominantly monomeric and have the capacity to nucleate aggregation of inert forms of tau in vitro and in cells. Finally, we used crosslinking mass spectrometry to identify the topological changes in tau as it converts from an inert state to a pathogenic seed. Future studies will reveal the relationship between soluble seeds and structural polymorphs derived from tauopathies to help diagnose and develop therapeutics targeting specific tauopathies.