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The accessory light-harvesting polypeptides associated with photosystem I (LHCI) in Porphyridium cruentum bind chlorophyll a, zeaxanthin and -carotene. A cDNA library of P. cruentum was screened with an antiserum specific to the LHCI polypeptides, and an 0.9 kb fragment was identified as coding for an LHCI polypeptide. This cDNA, which we named LhcaR1, has an open reading frame encoding 222 amino acid residues including a putative transit peptide of 28 amino acids. Hydropathy analysis suggests that there are three transmembrane helices in the mature polypeptide. Each of the amino acid residues that bind chlorophyll (six residues) and serve in stabilizing the helices in higher-plant LHCs are conserved in helices 1 and 3 of P. cruentum LhcaR1. The N-terminal flanking regions of these two helices also show high sequence conservation with other LHCs. Helix 2 contains a seventh putative chlorophyll-binding site, but resembles helix 2 of higher-plant LHCs to a lesser degree. A sequence motif of 11 residues found near the N-terminus and in each of the three helices suggests the possibility that the red algal LhcaR1 derives from a gene duplication. Polypeptides of the expected molecular weight in six other red algae (Achrochaetium, Bangia, Callithamnion, Cyanidium, Polysiphonia, Spermothamnion) were recognized by the antiserum to P. cruentum LHCI, indicating a wide distribution of LHCI in rhodophytes. 相似文献
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Absence of Ribonucleic Acid Methylase in the Avian Myeloblastosis Virus Core 总被引:1,自引:0,他引:1 下载免费PDF全文
N(2)-guanine-ribonucleic acid-methyltransferase, which is associated with avian myeloblastosis virus, is not a component of the viral core. 相似文献
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Raymond Gantt Frida Montes De Oca Virgina J. Evans 《In vitro cellular & developmental biology. Plant》1973,8(4):288-294
Summary Comparisons of nucleic acid methylation between paired neoplastic and non-neoplastic mouse cell lines have shown a striking
difference in the deoxyribonucleic acid (DNA) peak eluted from methylated albumin-kieselguhr columns (R. Gantt and V. J. Evans,
1969, Cancer Res. 29: 536–541). Since mouse satellite DNA is relatively highly methylated, its 5-methylcytosine content was
compared with mainband DNA in these two paired cell lines to determine whether this might account for the observed differences.
The cell DNA was labeled with methyl-labeled methionine and isolated from the cells by repeated neutral cesium chloride isopycnic
centrifugation. The satellite DNA strands were then separated in an alkaline cesium chloride gradient. Both the 5-methylcytosine
content and the relative amounts of satellite DNA were indistinguishable in the paired cell lines. Further, the results showed
that both strands of satellite DNA had virtually equal amounts of 5-methylcytosine, although the heavy strand contains 1.5
times more cytosine than the light strand. 相似文献
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M A Schoenbeck D A Samac M Fedorova R G Gregerson J S Gantt C P Vance 《Molecular plant-microbe interactions : MPMI》1999,12(10):882-893
Development of root nodules, specifically induction of cortical cell division for nodule initiation, requires expression of specific genes in the host and microsymbiont. A full-length cDNA clone and the corresponding genomic clone encoding a MAP (mitogen-activated protein) kinase homolog were isolated from alfalfa (Medicago sativa). The genomic clone, TDY1, encodes a 68.9-kDa protein with 47.7% identity to MMK4, a previously characterized MAP kinase homolog from alfalfa. TDY1 is unique among the known plant MAP kinases, primarily due to a 230 amino acid C-terminal domain. The putative activation motif, Thr-Asp-Tyr (TDY), also differs from the previously reported Thr-Glu-Tyr (TEY) motif in plant MAP kinases. TDY1 messages were found predominantly in root nodules, roots, and root tips. Transgenic alfalfa and Medicago truncatula containing a chimeric gene consisting of 1.8 kbp of 5' flanking sequence of the TDY1 gene fused to the beta-glucuronidase (GUS) coding sequence exhibited GUS expression primarily in the nodule parenchyma, meristem, and vascular bundles, root tips, and root vascular bundles. Stem internodes stained intensely in cortical parenchyma, cambial cells, and primary xylem. GUS activity was observed in leaf mesophyll surrounding areas of mechanical wounding and pathogen invasion. The promoter was also active in root tips and apical meristems of transgenic tobacco. Expression patterns suggest a possible role for TDY1 in initiation and development of nodules and roots, and in localized responses to wounding. 相似文献
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A Phylogenetic Assessment of the Eukaryotic Light-Harvesting Antenna Proteins, with Implications for Plastid Evolution 总被引:1,自引:0,他引:1
D.G. Durnford J.A. Deane S. Tan G.I. McFadden E. Gantt B.R. Green 《Journal of molecular evolution》1999,48(1):59-68
The light-harvesting complexes (LHCs) are a superfamily of chlorophyll-binding proteins present in all photosynthetic eukaryotes.
The Lhc genes are nuclear-encoded, yet the pigment–protein complexes are localized to the thylakoid membrane and provide a marker
to follow the evolutionary paths of plastids with different pigmentation. The LHCs are divided into the chlorophyll a/b-binding proteins of the green algae, euglenoids, and higher plants and the chlorophyll a/c-binding proteins of various algal taxa. This work examines the phylogenetic position of the LHCs from three additional taxa:
the rhodophytes, the cryptophytes, and the chlorarachniophytes. Phylogenetic analysis of the LHC sequences provides strong
statistical support for the clustering of the rhodophyte and cryptomonad LHC sequences within the chlorophyll a/c-binding protein lineage, which includes the fucoxanthin–chlorophyll proteins (FCP) of the heterokonts and the intrinsic peridinin–chlorophyll
proteins (iPCP) of the dinoflagellates. These associations suggest that plastids from the heterokonts, haptophytes, cryptomonads,
and the dinoflagellate, Amphidinium, evolved from a red algal-like ancestor. The Chlorarachnion LHC is part of the chlorophyll a/b-binding protein assemblage, consistent with pigmentation, providing further evidence that its plastid evolved from a green
algal secondary endosymbiosis. The Chlorarachnion LHC sequences cluster with the green algal LHCs that are predominantly associated with photosystem II (LHCII). This suggests
that the green algal endosymbiont that evolved into the Chlorarachnion plastid was acquired following the emergence of distinct LHCI and LHCII complexes.
Received: 25 February 1998 / Accepted: 13 May 1998 相似文献
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