发布: 2017年03月20日第7卷第6期 DOI: 10.21769/BioProtoc.2191 浏览次数: 11051
评审: Scott A M McAdamAgnieszka ZienkiewiczAnonymous reviewer(s)
Abstract
This protocol describes a method to extract ribulose-1,5-bisphosphate carboxylase oxygenase (Rubisco) from diatoms (Bacillariophyta) to determine catalytic performance. This protocol has been adapted from use in cyanobacteria and higher plants (Andrews, 1988; Whitney and Sharwood, 2007). First part (steps A1-A3) of the extraction provides a crude extract of Rubisco that is sufficient for carboxylation assays to measure the Michaelis constant for CO2 (KC) and the catalytic turnover rate (kcatc). However, the further purification steps outlined (steps B1-B4) are needed for measurements of Rubisco CO2/O2 Specificity (SC/O, [Kane et al., 1994]).
Keywords: Rubisco (Rubisco)Background
Ribulose-1,5-bisphosphate carboxylase oxygenase (Rubisco, EC 4.1.1.39) catalyzes the first step in the photosynthetic assimilation of CO2 and thus plays a fundamental role in photosynthesis and the global carbon cycle. Rubisco has been isolated from a wide range of organisms, from archaea, bacteria, algae to plants, and displays a diverse range of kinetics between organisms (Galmes et al., 2014; Tcherkez et al., 2006; Whitney et al., 2011). Knowledge of Rubisco kinetics is a key component for understanding how photosynthesis and thus the biological sink of carbon will respond to rising anthropogenic CO2. Diatoms are a group of unicellular algae responsible for ~20% of global photosynthesis (Falkowski and Raven, 2007) but as yet have been relatively poorly studied in terms of their Rubisco kinetics.
Isolation and purification of Rubisco is required before kinetic assays can be undertaken. Due to differences in cell structure and organic composition between organisms, the method for the purification of viable Rubisco enzyme needs to be continually optimized. This protocol describes a method to extract and purify Rubisco using size exclusion chromatography from diatoms in preparation for kinetic assays. The method is similar to Whitney and Sharwood (2007), used for the purification of Rubisco overexpressed in E. coli, in that a French press is used to mechanically rupture cells. The French press is necessary to obtain sufficient cell lysis as diatoms are unicellular with silica frustules, unlike plant tissue in which sufficient lysis is easily achieved by homogenizing frozen leaf tissue in a mortar and pestle. Furthermore, due to the low in vivo concentrations of Rubisco in diatoms (Losh et al., 2013), large diatom culture volumes concentrated via centrifugation, are needed to obtain enough biomass compared to plant tissue and E. coli lines with overexpressed Rubisco.
Materials and Reagents
Note: All chemicals are of A.C.S. grade.
Equipment
Procedure
文章信息
版权信息
© 2017 The Authors; exclusive licensee Bio-protocol LLC.
如何引用
Young, J. N., Heureux, A. M. C., Rickaby, R. E. M., Morel, F. M. M., Whitney, S. M. and Sharwood, R. E. (2017). Rubisco Extraction and Purification from Diatoms. Bio-protocol 7(6): e2191. DOI: 10.21769/BioProtoc.2191.
分类
植物科学 > 植物生理学 > 光合作用
生物化学 > 其它化合物 > 叶绿素
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