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PNAS:揭示鞭毛藻在光合作用中的自我保护机制

来源:生命经纬 2009-12-15 09:27

鞭毛藻

细胞如果在光照强度很高的条件下进行光合作用,将会产生一种极危险的氧自由基。但是在鞭毛藻(Dinoflagellates)细胞内,却有一种独特的光捕获复合体(light-harvesting  complex),能够将多余能量有效地转化为其他形式的能量,从而避免细胞损伤。最近,一项由美国和捷克的生物物理学家共同完成的研究中,发现了在光捕获复合体能量转化过程中的一种重要的分子。这项研究发表在最近的PNAS杂志上。

鞭毛藻是一种重要的海洋浮游生物,生活在10米以下的海水中,鞭毛藻有一个重要的特征,能够利用一种类胡萝卜素——甲藻素(peridinin)作为光捕获色素。甲藻素能够吸收从海水表面辐射到其生存环境中一定波长的光。鞭毛藻的光捕获复合体结构很特别,以一个叶绿素分子为中心,四周聚集着四个甲藻素分子,从而形成甲藻素-叶绿素蛋白(peridinin-chlorophyll-protein,PCP),甲藻素能够捕获光能,并将光能高效地转移到中心的叶绿素分子上,研究人员推测,转移到叶绿素分子上的能量还会转移到其它光捕获蛋白中,最终进入中心光系统实现能量的转换并产生氧气。(生物谷Bioon.com)

生物谷推荐原始出处:

PNAS November 23, 2009, doi: 10.1073/pnas.0908938106

Identification of a single peridinin sensing Chl-a excitation in reconstituted PCP by crystallography and spectroscopy

Tim Schultea,1, Dariusz M. Niedzwiedzkib,1,2, Robert R. Birgeb, Roger G. Hillerc, Tomá? Polívkad,e, Eckhard Hofmanna,3 and Harry A. Frankb,3

aBiophysics, Department of Biology and Biotechnology, Ruhr-University Bochum, D-44780 Bochum, Germany;
bDepartment of Chemistry, University of Connecticut, Storrs, CT 06269-3060;
cBiology Department, Faculty of Science, Macquarie University, NSW 2109, Australia;
dInstitute of Physical Biology, University of South Bohemia, 373-33 Nove Hrady, Czech Republic; and
eBiological Centre, Czech Academy of Sciences, Ceske Budejovice, Czech Republic

The peridinin-chlorophyll a-protein (PCP) of dinoflagellates is unique among the large variety of natural photosynthetic light-harvesting systems. In contrast to other chlorophyll protein complexes, the soluble PCP is located in the thylakoid lumen, and the carotenoid pigments outnumber the chlorophylls. The structure of the PCP complex consists of two symmetric domains, each with a central chlorophyll a (Chl-a) surrounded by four peridinin molecules. The protein provides distinctive surroundings for the pigment molecules, and in PCP, the specific environment around each peridinin results in overlapping spectral line shapes, suggestive of different functions within the protein. One particular Per, Per-614, is hypothesized to show the strongest electronic interaction with the central Chl-a. We have performed an in vitro reconstitution of pigments into recombinant PCP apo-protein (RFPCP) and into a mutated protein with an altered environment near Per-614. Steady-state and transient optical spectroscopic experiments comparing the RFPCP complex with the reconstituted mutant protein identify specific amino acid-induced spectral shifts. The spectroscopic assignments are reinforced by a determination of the structures of both RFPCP and the mutant by x-ray crystallography to a resolution better than 1.5 ?. RFPCP and mutated RFPCP are unique in representing crystal structures of in vitro reconstituted light-harvesting pigment-protein complexes.

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