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Cuticle-degrading serine protease Ver112, which derived from a nematophagous fungus Lecanicillium psalliotae, has been exhibited to have high cuticle-degrading and nematicidal activities. We have performed molecular dynamics (MD) simulation based on the crystal structure of Ver112 to investigate its dynamic properties and large-scale concerted motions. The results indicate that the structural core of Ver112 shows a small fluctuation amplitude, whereas the substrate binding sites, and the regions close to and opposite the substrate binding sites experience significant conformational fluctuations. The large concerted motions obtained from essential dynamics (ED) analysis of MD trajectory can lead to open or close of the substrate binding sites, which are proposed to be linked to the functional properties of Ver112, such as substrate binding, orientation, catalytic, and release. The significant motion in the loop regions that is located opposite the binding sites are considered to play an important role in modulating the dynamics of the substrate binding sites. Furthermore, the bottom of free energy landscape (FEL) of Ver112 are rugged, which is mainly caused by the fluctuations of substrate binding regions and loops located opposite the binding site. In addition, the mechanism underlying the high flexibility and catalytic activity of Ver112 was also discussed. Our simulation study complements the biochemical and structural studies, and provides insight into the dynamics-function relationship of cuticle-degrading serine protease Ver112.  相似文献
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Stomatal closure and metabolic impairment under drought stress limits photosynthesis. The objective of this study was to determine major stomatal and metabolic factors involved in photosynthetic responses to drought and recovery upon re‐watering in a C3 perennial grass species, Kentucky bluegrass (Poa pratensis L.). Two genotypes differing in drought resistance, ‘Midnight’ (tolerant) and ‘Brilliant’ (sensitive), were subjected to drought stress for 15 days and then re‐watered for 10 days in growth chambers. Single‐leaf net photosynthetic rate (A), stomatal conductance (gs) and transpiration rate (Tr) decreased during drought, with a less rapid decline in ‘Midnight’ than in ‘Brilliant’. Photochemical efficiency, Rubisco activity and activation state declined during drought, but were significantly higher in ‘Midnight’ than in ‘Brilliant’. The relationship between A and internal leaf CO2 concentration (A/Ci curve) during drought and re‐watering was analyzed to estimate the relative influence of stomatal and non‐stomatal components on photosynthesis. Stomatal limitation (Ls %), non‐stomatal limitation (Lns %), CO2 compensation point (CP) and dark respiration (Rd) increased with stress duration in both genotypes, but to a lesser extent in ‘Midnight’. Maximum CO2 assimilation rate (Amax), carboxylation efficiency (CE) and mesophyll conductance (gm) declined, but ‘Midnight’ had significantly higher levels of Amax, CE and gm than ‘Brilliant’. Maximum carboxylation rate of Rubisco (Vcmax) and ribulose‐1,5‐bisphospate (RuBP) regeneration capacity mediated by maximum electron transport rate (Jmax) decreased from moderate to severe drought stress in both genotypes, but to a greater extent in ‘Brilliant’ than in ‘Midnight’. After re‐watering, RWC restored to about 90% of the control levels in both genotypes, whereas A, gs, Tr and Fv/Fm was only partially recovered, with a higher recovery level in ‘Midnight’ than in ‘Brilliant’. Rubisco activity and activation state restored to the control level after re‐watering, with more rapid increase in ‘Midnight’ than in ‘Brilliant’. The values of Ls, Lns, CP and Rd declined, and Amax, CE, Vcmax, Jmax and gm increased after re‐watering, with more rapid change in all parameters in ‘Midnight’ than in ‘Brilliant’. These results indicated that the maintenance of higher A and Amax under drought stress in drought‐tolerant Kentucky bluegrass could be attributed to higher Rubico activation state, higher CE and less stomatal limitation. The ability to resume metabolic activity (Amax, CE, Fv/Fm and Rubisco) was observed in the drought‐tolerant genotype and is the most likely cause for the increased recuperative ability of photosynthesis. Incomplete recovery of photosynthesis upon re‐watering could be attributable to lasting stomatal limitations caused by severe drought damage in both genotypes. Promoting rapid stomatal recovery from drought stress may be critical for plants to resume full photosynthetic capacity in C3 perennial grass species.  相似文献
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