The Topology of the Plastoquinone and Herbicide Binding Peptides of Photosystem II in the Thylakoid Membrane

1986 ◽  
Vol 41 (1-2) ◽  
pp. 240-246 ◽  
Author(s):  
Achim Trebst

Abstract The 32 kDa herbicide and QB binding peptide (D-1 protein) and its homologous 34 kDa peptide (D-2 protein) are integral membrane subunits of photosystem II. A model for their folding through the thylakoid membrane in five transmembrane a-helices is proposed from the compari­son of amino acid sequence and hydropathy index plot homologies with subunits of the bacterial system. Following recent data on the X-ray structure of a bacterial photosystem the binding niche for QB is interpreted on the basis of the amino acid changes found in the 32 kDa peptide in herbicide tolerant higher plants and algae.

1998 ◽  
Vol 123 (4) ◽  
pp. 493-499 ◽  
Author(s):  
Kyu H. Chung ◽  
Dennis E. Buetow ◽  
Schuyler S. Korban

A nuclear gene, Lhcb1*Pp1, encoding a light-harvesting chlorophyll a/b-binding protein of photosystem II has been isolated from peach [Prunus persica (L.) Batsch. `Stark Earliglo'] leaf genomic DNA, cloned, and sequenced. This gene encodes a precursor polypeptide of 267 amino acids with a transit peptide of 34 and a type I mature protein of 233 amino acids. The amino acid sequence of the mature polypeptide is 89% to 94% and 80% to 94% similar to those encoded by type I Lhcb genes of annual and other woody plants, respectively. In contrast, the amino acid sequence of the peach transit peptide is less conserved being 47% to 69% similar to those of annual plants and only 17% to 22% similar to those of other woody plants. The peach gene was used as a probe for Lhcb gene expression. Lhcb mRNA is detected in leaves of field-grown trees during June to October. Lhcb mRNA is detected at a high level in leaves of peach shoots grown in tissue culture in the light, but only at a trace level in leaves grown in the dark. Some Lhcb genes appear to be light-modulated in stems. Lhcb1*Ppl contains four potential polyadenylation sites. S1 nuclease analysis detected transcripts of the sizes expected from each of the four polyadenylation sites. All four are found in leaves of light-grown shoots and of field-grown trees throughout the growing season. In contrast, only three are detected in stems of light-grown shoots.


The complete amino acid sequence of yeast phosphoglycerate mutase comprising 241 residues has been determined. The sequence was deduced from the two cyanogen bromide fragments, and from the peptides derived from these fragments after digestion by a number of proteolytic enzymes. Determination of this sequence now allows a detailed interpretation of the existing high-resolution X-ray crystallographic structure. A comparison of the sequence reported here with the sequences of peptides from phosphoglycerate mutases from other species, and with the sequence of erythrocyte diphosphoglycerate mutase, indicates that these enzymes have a high degree of structural homology. Autolysis of phosphoglycerate mutase by yeast extracts leads to the complete loss of mutase activity, and the formation of electrophoretically distinguishable forms (R. Sasaki, E. Sugimoto & H. Chiba, Archs Biochem. Biophys. 115, 53-61 (1966)). It is apparent from the amino acid sequence that these changes are due to the loss of an 8─12 residue peptide from the C-terminus.


1987 ◽  
Vol 42 (6) ◽  
pp. 742-750 ◽  
Author(s):  
Achim Trebst

The folding through the membrane of the plastoquinone and herbicide binding protein subunits of photosystem II and the topology of the binding niche for plastoquinone and herbicides is described. The model is based on the homology in amino acid sequence and folding prediction from the hydropathy analysis of the D-1 and D-2 subunits of photosystem II to the reaction center polypeptides L and M of the bacterial reaction center. It incorporates the amino acid changes in the D-1 polypeptide in herbicide tolerant plants and those indicated by chemical tagging to be involved in Qв binding. It proposes homologous amino acids in the D-1/D-2 polypeptides to those indicated by the X-ray structure of the bacterial reaction center to be involved in Fe-, quinone- and reaction center chlorophyll-binding. The different chemical compounds known to interfere with Qв function are grouped into two families depending on their orientation in the Qв binding niche.


2002 ◽  
Vol 362 (1) ◽  
pp. 131-135 ◽  
Author(s):  
Michael ARAND ◽  
Alexander M. GOLUBEV ◽  
J. R. Brandao NETO ◽  
Igor POLIKARPOV ◽  
R. WATTIEZ ◽  
...  

Extracellular exo-inulinase has been isolated from a solid-phase culture of the filamentous fungus Aspergillus awamori var. 2250. The apparent molecular mass of the monomer enzyme was 69±1kDa, with a pI of 4.4 and a pH optimum of 4.5. The enzyme hydrolysed the β-(2 → 1)-fructan (inulin) and β-(2 → 6)-fructan (levan) via exo-cleavage, releasing fructose. The values for the Michaelis constants Km and Vmax in the hydrolysis of inulin were 0.003±0.0001mM and 175±5μmol·min−1·mg−1. The same parameters in the hydrolysis of levan were 2.08±0.04mg/ml and 1.2±0.02μmol/min per mg, respectively. The gene and cDNA encoding the A. awamori exo-inulinase were cloned and sequenced. The amino acid sequence indicated that the protein belongs to glycoside hydrolase family 32. A surprisingly high similarity was found to fructosyltransferase from Aspergillus foetidus (90.7% on the level of the amino acid sequence), despite the fact that the latter enzyme is unable to hydrolyse inulin and levan. Crystals of the native exo-inulinase were obtained and found to belong to the orthorhombic space group P212121 with cell parameters a = 64.726 Å (1Å = 0.1 nm), b = 82.041 Å and c = 136.075 Å. Crystals diffracted beyond 1.54 Å, and useful X-ray data were collected to a resolution of 1.73 Å.


1991 ◽  
Vol 46 (7-8) ◽  
pp. 557-562 ◽  
Author(s):  
A. Trebst

Abstract A new contact site between the two reaction center polypeptides D 1 and D 2 of photosystem II close to arg 238 and arg 234 respectively is proposed. The amino acid sequences involved are between the 4 th transmembrane and a connecting parallel helix. The sequence includes a tryp­ sin sensitive site in both polypeptides, the likely cleavage site in the rapid turnover of the D 1 polypeptide and part of the herbicide binding site. The contact site is oriented towards both quinone binding sites Q A and Q B. A folding of the backbone of the amino acid sequences involved is proposed.


The positively stained bands of the segment long spacing (s. l. s.) pattern of collagen are shown to be accounted for by the distribution of charged residues in the sequence of the α 1 chain. The native tendon pattern can be constructed by repeated stagger of 234 residues between adjacent molecules, as in the Hodge-Petruska model. The relation of the precise version of this model to negatively stained patterns is shown and the part played by the teleopeptides revealed. A brief discussion of the meridional X-ray reflexions in terms of amino acid sequence is presented and related to electron microscope patterns. Optical diffraction suggests an approximate thirding of the D period. Finally a symmetric structure formed by reconstituting chick cartilage collagen is analysed and its origins revealed as an elaboration of the Hodge-Petruska model. It is shown to be related to the fibrous long spacing (f. l. s. I) structure.


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