Sukenik Assaf, Livne Alexander, Apt Kirk E, Grossman Arthur R
National Institute of Oceanography, Israel Oceanographic and Limnological Research, Haifa 31080, IsraelMartek Biosciences Corporation, Columbia, Maryland 21045The Carnegie Institution of Washington, Department of Plant Biology, Stanford, California 94305.
J Phycol. 2000 Jun;36(3):563-570. doi: 10.1046/j.1529-8817.2000.99115.x. Epub 2001 Dec 25.
In contrast to vascular plants, green algae, and diatoms, the major light-harvesting complex of the marine eustigmatophyte genus Nannochloropsis is a violaxanthin-chlorophyll a protein complex that lacks chlorophylls b and c. The isolation of a single polypeptide from the light-harvesting complex of Nannochloropsis sp. (IOLR strain) was previously reported (Sukenik et al. 1992). The NH -terminal amino acid sequence of this polypeptide was significantly similar to NH -terminal sequences of the light-harvesting fucoxanthin, chlorophyll a/c polypeptides from the diatom Phaeodactylum tricornutum Bohlin. Using polyclonal antibodies raised to the Nannochloropsis light-harvesting polypeptide, a gene encoding this polypeptide was isolated from a cDNA expression library. The deduced amino acid sequence of the Nannochloropsis violaxanthin-chlorophyll a polypeptide reveals a 36 amino acid presequence followed by 173 amino acids that constitute the mature polypeptide. The mature polypeptide has 30%-40% sequence identity to the diatom fucoxanthin-chlorophyll a/c polypeptides and less then 27% identity to the green algal and vascular plant light-harvesting chlorophyll polypeptides that bind both chlorophylls a and b. Its molecular mass, as deduced from the gene sequence, is 18.4 kDa with three putative transmembrane helices and several residues that may be involved in chlorophyll binding. The cDNA encoding the violaxanthin-chlorophyll a polypeptide was used to isolate and characterize a 10 kb genomic fragment containing the entire gene. The open reading frame was interrupted by five introns ranging in size from 123 to 449 bp. The intron borders have typical eukaryotic GT … AG sequences.
与维管植物、绿藻和硅藻不同，海洋真眼点藻属微绿球藻的主要捕光复合体是一种叶黄素 - 叶绿素a蛋白复合体，缺乏叶绿素b和c。此前已有报道从微绿球藻（IOLR菌株）的捕光复合体中分离出一种单一多肽（Sukenik等人，1992年）。该多肽的N端氨基酸序列与硅藻三角褐指藻的捕光岩藻黄素 - 叶绿素a/c多肽的N端序列显著相似。利用针对微绿球藻捕光多肽产生的多克隆抗体，从cDNA表达文库中分离出编码该多肽的基因。微绿球藻叶黄素 - 叶绿素a多肽的推导氨基酸序列显示，其前导序列有36个氨基酸，随后是构成成熟多肽的173个氨基酸。成熟多肽与硅藻岩藻黄素 - 叶绿素a/c多肽的序列同一性为30% - 40%，与结合叶绿素a和b的绿藻和维管植物捕光叶绿素多肽的同一性小于27%。从基因序列推导，其分子量为18.4 kDa，有三个推定的跨膜螺旋和几个可能参与叶绿素结合的残基。编码叶黄素 - 叶绿素a多肽的cDNA被用于分离和鉴定一个包含整个基因的10 kb基因组片段。开放阅读框被5个大小从123到449 bp的内含子打断。内含子边界具有典型的真核生物GT…AG序列。
