Structural basis of polyamine transport by human ATP13A2 (PARK9)

Polyamines are small, organic polycations that are ubiquitous and essential to all forms of life. Currently, how polyamines are transported across membranes is not understood. Recent studies have suggested that ATP13A2 and its close homologs, collectively known as P5B-ATPases, are polyamine transporters at endo-/lysosomes. Loss-of-function mutations of ATP13A2 in humans cause hereditary early-onset Parkinson's disease. To understand the polyamine transport mechanism of ATP13A2, we determined high-resolution cryo-EM structures of human ATP13A2 in five distinct conformational intermediates, which together represent a near-complete transport cycle of ATP13A2. The structural basis of the polyamine specificity was revealed by an endogenous polyamine molecule bound to a narrow, elongated cavity within the transmembrane domain. The structures show an atypical transport path for a water-soluble substrate, where polyamines may exit within the cytosolic leaflet of the membrane. Our study provides important mechanistic insights into polyamine transport and a framework to understand functions and mechanisms of P5B-ATPases.

In vitro Gas Production, Methane Emission and Rumen Fermentation Characteristics with Increasing Roughage to Concentrate Ratios

Effects of roughage to concentrate ratio on gas production (GP) and nutrient degradability were evaluated in vitro. Rations I: 0R:100C, II: 20R:80C, III: 40R:60C, IV: 60R:40C, V: 80R:20C and VI: 100R:0C were incubated for 24h. Concentrate (0R:100C) produced greater GP/gDM, TDOM and MCP. TDDM was higher for rations I to IV than V and VI. Roughage (100R:0C) had lower PF and higher pH and protozoal count with no VFA effect. Ration III and IV containing 60 and 40% concentrate, respectively exhibited balanced distribution of soluble substrate between microbial biomass production and fermentation waste products and are optimal for sheep nutrition.

AKTIVITAS AKTINOMISETES DARI BANGKA-BELITUNG KOLEKSI BIDANG MIKROBIOLOGI, PUSLIT BIOLOGI- LIPI DALAM MEMPRODUKSI ENZIM KITINASE

The aim of the research was to know the capability of actinomycetes isolate from Bangka Belitung, which stored at Microbiology-LIPI Culture Collection, in producing chitinase enzyme. This isolate which could produce chitinolitic enzyme, signed by clear zone at medium contain 1% chitine. The chitinase activity of the isolate which incubated for 1-7 days in the room temperature was analyzed by spectrophotometer in λ 584 nm. The result of this experiment was highest chitinase activities with incubated for 3 days, were 1.66 . 10-2 U/ml. Maximum chitinase activities was found at 1% starch soluble substrate 2.83 . 10-2, pH 8.0 and at 50°C condition were 9.3 . 10-2 and 12.98 .10-2 U/ml respectively.Key words : chitinase, clear zone, spectrophotometer

Modeling of organic substrate transformation in the high-rate activated sludge process

This study describes the development of a modified activated sludge model No.1 framework to describe the organic substrate transformation in the high-rate activated sludge (HRAS) process. New process mechanisms for dual soluble substrate utilization, production of extracellular polymeric substances (EPS), absorption of soluble substrate (storage), and adsorption of colloidal substrate were included in the modified model. Data from two HRAS pilot plants were investigated to calibrate and to validate the proposed model for HRAS systems. A subdivision of readily biodegradable soluble substrate into a slow and fast fraction were included to allow accurate description of effluent soluble chemical oxygen demand (COD) in HRAS versus longer solids retention time (SRT) systems. The modified model incorporates production of EPS and storage polymers as part of the aerobic growth transformation process on the soluble substrate and transformation processes for flocculation of colloidal COD to particulate COD. The adsorbed organics are then converted through hydrolysis to the slowly biodegradable soluble fraction. Two soluble substrate models were evaluated during this study, i.e., the dual substrate and the diauxic models. Both models used two state variables for biodegradable soluble substrate (SBf and SBs) and a single biomass population. The A-stage pilot typically removed 63% of the soluble substrate (SB) at an SRT <0.13 d and 79% at SRT of 0.23 d. In comparison, the dual substrate model predicted 58% removal at the lower SRT and 78% at the higher SRT, with the diauxic model predicting 32% and 70% removals, respectively. Overall, the dual substrate model provided better results than the diauxic model and therefore it was adopted during this study. The dual substrate model successfully described the higher effluent soluble COD observed in the HRAS systems due to the partial removal of SBs, which is almost completely removed in higher SRT systems.