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E Pichersky

Publications and source records attributed to E Pichersky.

At least 37 records · Page 2Linked to original sources
PubMed1996

Cold-sensitive assembly of a mutant manganese-stabilizing protein caused by a Val to Ala replacement.

Photosystem II (PSII) is a multisubunit transmembrane protein complex that oxidizes water and evolves O2. A tetranuclear manganese cluster associated with integral membrane subunits of PSII catalyzes water oxidation. The 33-kDa water-soluble PSII subunit, or manganese-stabilizing protein (MSP), stabilizes the O2-evolving manganese cluster and accelerates O2 evolution. Spinach PSII can be depleted of native MSP under conditions which retain a functional manganese cluster. Reconstition of MSP-depleted PSII with recombinant MSP was equally efficient at 4 and 22 degrees C. Replacement of Val235 (a conserved residue near the C-terminus of MSP) with Ala inhibited assembly of MSP at 4 degrees C, but not at 22 degrees C. Once assembled, [V235A]MSP remained bound to PSII even at 4 degrees C and in the presence of low concentrations of urea. Results from far-UV circular dichroism spectrometry indicated that [V235A]-MSP was destabilized by low temperature to a greater extent than the wild-type protein. However, the effect of temperature on the secondary structure of both the mutant and wild-type proteins was small compared to the temperature-independent destabilization of secondary structure induced by the mutation. These results demonstrate that the V235A mutation introduces an activation energy barrier for assembly of MSP into PSII, and it is suggested that the mutation acts by inhibiting isomerization of one or more prolyl peptide bonds required for assembly.

Amino Acid Sequence↗
PubMed1996

Evolution of floral scent in Clarkia: novel patterns of S-linalool synthase gene expression in the C. breweri flower.

Flowers of Clarkia breweri, an annual plant from the coastal range of California, emit a strong sweet scent of which S-linalool, an acyclic monoterpene, is a major component. Chromosomal, chemical, and morphological data, and the species' geographic distribution, suggest that C. breweri evolved from an extant nonscented species, C. concinna. A cDNA of Lis, the gene encoding S-linalool synthase, was isolated from C. breweri. We show that in C. breweri, Lis is highly expressed in cells of the transmitting tract of the stigma and style and in the epidermal cells of petals, as well as in stamens, whereas in the nonscented C. concinna, Lis is expressed only in the stigma and at a relatively low level. In both species, changes in protein levels parallel changes in mRNA levels, and changes in enzyme activity levels parallel changes in protein levels. The results indicate that in C. breweri, the expression of Lis has been upregulated and its range enlarged to include cells not expressing this gene in C. concinna. These results show how scent can evolve in a relatively simple way without the evolution of highly specialized "scent glands" and other specialized structures. Lis encodes a protein that is structurally related to the family of proteins termed terpene synthases. The protein encoded by Lis is the first member of this family found to catalyze the formation of an acyclic monoterpene.

Acyclic Monoterpenes↗
PubMed1995

Purification and characterization of S-linalool synthase, an enzyme involved in the production of floral scent in Clarkia breweri.

S-Linalool is one of the volatiles emitted by Clarkia breweri Grey [Green] flowers to attract its moth pollinator. S-Linalool synthase, the enzyme that stereoselectively converts the ubiquitous C10 intermediate GPP to S-linalool, is abundant in stigmata of freshly opened flowers, and it was purified to > 95% homogeneity by anion-exchange and hydroxyapatite chromatography. S-Linalool synthase is operationally soluble as are other monoterpene synthases, has a Km of 0.9 microM for geranyl pyrophosphate, exhibits a strict requirement for a divalent metal cofactor with a preference for Mn2+ (Km = 45 microM), and shows an optimal pH of 7.4. The enzyme is active as a monomer of 76 +/- 3 kDa as determined by gel permeation chromatography and polyacrylamide gel electrophoresis. Neither S- nor R-linalyl pyrophosphates are substrates for the C. breweri S-linalool synthase, although this tertiary allylic pyrophosphate ester is a bound intermediate in the biosynthesis of cyclic monoterpenes from geranyl pyrophosphate in many plant species, where it also serves as an alternate substrate.

Acyclic Monoterpenes↗
PubMed1994

Topological studies of spinach 22 kDa protein of Photosystem II.

An intrinsic 22 kDa polypeptide is associated with the O2-evolving Photosystem II core complex in a variety of green plants, although it does not appear to be required for O2 evolution. Digestion of thylakoid membranes and isolated Photosystem II preparations with trypsin, followed by immunoblotting using spinach anti-22 kDa antibodies, leads to two observations: (1) the domain between the 2nd and 3rd transmembrane helices of the 22 kDa protein is stromally exposed, and (2) only in a reaction center complex preparation, lacking the chlorophyll a/b-light harvesting complex II, is there extensive proteolytic cleavage of the 22 kDa protein. We also found that after, but not prior to, selective extraction of the 22 and 10 kDa proteins from Photosystem II membranes, the chlorophyll a/b-light harvesting complex II can be separated from the Photosystem II reaction center core by precipitation with MgCl2. This result suggests that the 22 kDa polypeptide is located between the Photosystem II reaction center polypeptides and light-harvesting complex II; it is possible that the protein serves as a link between the two protein complexes. The presence of the 22 kDa protein in several species was also examined by immunoblotting with polyclonal spinach anti-22 kDa antibodies.

Amino Acid Sequence↗
PubMed1994

Reconstitution of the spinach oxygen-evolving complex with recombinant Arabidopsis manganese-stabilizing protein.

The psbO gene of cyanobacteria, green algae and higher plants encodes the precursor of the 33 kDa manganese-stabilizing protein (MSP), a water-soluble subunit of photosystem II (PSII). Using a pET-T7 cloning/expression system, we have expressed in Escherichia coli a full-length cDNA clone of psbO from Arabidopsis thaliana. Upon induction, high levels of the precursor protein accumulated in cells grown with vigorous aeration. In cells grown under weak aeration, the mature protein accumulated upon induction. In cells grown with moderate aeration, the ratio of precursor to mature MSP decreased as the optical density at induction increased. Both forms of the protein accumulated as inclusion bodies from which the mature protein could be released under mildly denaturing conditions that did not release the precursor. Renatured Arabidopsis MSP was 87% as effective as isolated spinach MSP in restoring O2 evolution activity to MSP-depleted PSII membranes from spinach; however, the heterologous protein binds to spinach PSIIs with about half the affinity of the native protein. We also report a correction to the previously published DNA sequence of Arabidopsis psbO (Ko et al., Plant Mol Biol 14 (1990) 217-227).

Amino Acid Sequence↗
PubMed1993

Concerted circadian oscillations in transcript levels of nineteen Lha/b (cab) genes in Lycopersicon esculentum (tomato).

Steady-state mRNA levels of nineteen members of the Lha/b (cab) gene family of Lycopersicon esculentum, encoding nine different types of light-harvesting complex (LHC) polypeptides, were determined by primer extension analysis. Each Lha/b gene is expressed and individual mRNAs accumulate to distinct levels. The relative contribution of each Lha/b mRNA to the total Lha/b mRNA levels is very similar in different green organs (leaves, stems, fruits, sepals) and after light treatment of etiolated seedlings. Detailed analysis of Lha/b mRNA accumulation in leaves under light/dark conditions, continuous darkness and continuous light revealed diurnal and circadian oscillations of Lha/b mRNAs for all genes. Only minor instances of divergence from a general expression pattern are apparent. Together these results indicate a concerted expression of all genes, suggesting that similar or identical molecular mechanisms and signal transduction chain control the expression of all Lha/b genes.

Base Sequence↗
PubMed1993

Molecular characterization of duplicate cytosolic phosphoglucose isomerase genes in Clarkia and comparison to the single gene in Arabidopsis.

The nucleotide sequence of PgiC1-a which encodes a cytosolic isozymes of phosphoglucose isomerase (PGIC; EC 5.3.1.9) in Clarkia lewisii, a wildflower native to California, is described and compared to the previously published sequence of the duplicate PgiC2-a from the same genome. Both genes have the same structure of 23 exons and 22 introns located in identical positions, and they encode proteins of 569 amino acids. Exon and inferred protein sequences of the two genes are 96.4% and 97.2% identical, respectively. Intron sequences are 88.2% identical. The high nucleotide similarity of the two genes is consistent with previous genetic and biosystematic findings that suggest the duplication arose within Clarkia. A partial sequence of PgiC2-b was also obtained. It is 99.5% identical to PgiC2-a in exons and 99.7% in introns. The nucleotide sequence of the single PgiC from Arabidopsis thaliana was also determined for comparison to the Clarkia genes. The A. thaliana PgiC has 21 introns located at positions identical to those in Clarkia PgiC1 and PgiC2, but lacks the intron that divides Clarkia exons 21 and 22. The A. thaliana PGIC protein is shorter, with 560 amino acids, and differs by about 17% from the Clarkia PGICs. The PgiC in A. thaliana was mapped to a site 20 cM from restriction fragment length polymorphism marker 331 on chromosome 5.

Amino Acid Sequence↗
PubMed1992

Characterization of a spinach psbS cDNA encoding the 22 kDa protein of photosystem II.

An intrinsic 22 kDa polypeptide is found associated with the oxygen-evolving photosystem II (PSII) core complex in all green plants and cyanobacteria so far examined, although it does not appear to be required for oxygen evolution. Amino acid sequence information obtained from the purified 22 kDa protein was used to construct a probe that was employed to isolate a full-length cDNA clone encoding the 274-residue precursor of the 22 kDa protein. Hydropathy plot analysis predicts the existence of four membrane-spanning helices in the mature protein. The two halves of the approximately 200-residue mature protein show high sequence similarity to each other, suggesting that the psbS gene arose from an internal gene duplication. The 22 kDa protein has some sequence similarity to chlorophyll a/b-binding proteins.

Amino Acid Sequence↗
PubMed1992

Identification of the polypeptides of the major light-harvesting complex of photosystem II (LHCII) with their genes in tomato.

Using an improved SDS-PAGE system, the polypeptides of the major chlorophyll a/b light-harvesting complex of PSII (LHCII) from tomato leaves were resolved into five polypeptide bands. All the polypeptides were matched with the genes encoding them by comparing amino acid sequences of tryptic peptides with gene sequences. The two major LHCII bands (usually comigrating as a '27 kDa' polypeptide) were encoded by cab1 and cab3 (Type I LHCII) genes. A third strong band of about 25 kDa was encoded by cab4 (Type II) genes. Polypeptides from two minor bands of 23-24 kDa were not N-terminally blocked; their N-terminal sequences showed they were Type III LHCII proteins. One complete cDNA clone and several incomplete clones for Type III polypeptides were sequenced. Combined with the peptide sequences, the results indicate that there are at least four different Type III genes in tomato, encoding four almost identical polypeptides. Thus, all the LHCII CAB polypeptides have been identified, and each type of LHCII polypeptide is encoded by distinct gene or genes in tomato.

Amino Acid Sequence↗