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The nucleotide sequence of an 8 kbp region of pea (Pisum sativum L.) chloroplast DNA containing the rRNA operon and putative promoter sites has been determined and compared to the corresponding sequences from maize, tobacco and the liverwort Marchantia polymorpha. The chloroplast DNA species of all vascular plants investigated, with the exception of a few legumes including pea, and of Marchantia contain an inverted repeat with an rRNA operon. The pea rRNA operon is the first sequenced rRNA operon from a plant with only one copy of the rRNA genes per molecule of chloroplast DNA. The organization of the operon is the same as for maize, tobacco and Marchantia, i.e. tRNA-Val gene/16S rRNA gene/spacer with intron-containing genes for tRNA-Ile and tRNA-Ala/23S rRNA gene/4.5S rRNA gene/5S rRNA gene. Current evidence suggests that the tRNA-Val gene may not be contranscribed with the other genes. For pea 16S, 23S, 4.5S and 5S rRNA have 1488, 2813, 105 and 121 nucleotides, respectively. The homologies of the entire operon (the tRNA-Val gene-5S rRNA region) to those from tobacco, maize and Marchantia are 88, 82 and 79%, respectively. The corresponding homologies for tobacco/maize, tobacco/Marchantia and maize/Marchantia have similar values. The 16S and 23S rRNA genes from pea are more than 90% homologous to those from the 3 other species. We conclude that the fact that pea only has one set of rRNA genes per molecule of chloroplast DNA is apparently not correlated with any significant difference between the pea operon and the rRNA operons from tobacco, maize and Marchantia. [ABSTRACT FROM AUTHOR]

Tissue-specific expression of human UGT1A6, a UDP-glucuronosyltransferase isoform conjugating a wide variety of planar phenols, has been studied using a reverse transcriptase-polymerase chain reaction. Use of intron-overlapping forward and reverse primers from exon 1 and 2 and of a "hot start" modification led to selective amplification of a UGT1A6 mRNA fragment. In addition, homologous competitor mRNA was synthesized, reverse transcribed, and coamplified to allow quantitation of UGT1A6 mRNA. Using these methods UGT1A6 mRNA could be demonstrated in liver, kidney, duodenum, and lung. Cell-specific regulation of UGT1A6 by TCDD (2,3,7,8-tetrachlorodibenzo-p-dioxin) was studied in various cell systems. TCDD induction was found in the human colon carcinoma cell line Caco-2 and in hepatocyte primary cultures. In contrast, in lung carcinoma A549 cells this isoform was constitutively expressed and not induced by TCDD.

The essential role of cytochrome P450 3A4 (CYP3A4) in human small intestine is well established, and CYP3A5 seems also to be present in most subjects. However, the role of CYP3A7 in the small intestine remains poorly characterized. We have therefore studied the expression of these CYP3A enzymes in the duodenal tissue from 19 patients, using a specific RT-PCR (reverse transcriptase-polymerase chain reaction) method. CYP3A4 and CYP3A5 were present at the mRNA level in the duodenum of 18 and 19 of the 19 patients studied, respectively. In contrast, mRNA for CYP3A7 was not found in the duodenum in any of the patients. These findings strongly suggest that, unlike CYP3A4 and CYP3A5, CYP3A7 is not expressed in human duodenum.

Chromatofocusing of soybean (Glycine max L.) leaf lipoxygenases revealed three distinct peaks of activity. Based on their isoelectric points (pls), pH optima, and mutant analysis it appears that the leaf isozymes are different from those described from mature soybean seed. At least one leaf lipoxygenase appears to differ from those found in hypocotyls. The pls of the main bands of the three leaf lipoxygenase peaks are 6.67, 5.91, and 5.67. The pH optima curves of three active fractions exhibit peaks at pH 6.2, 5.5, and 8.5, respectively. One of the fractions has two polypeptides with slightly different molecular weights, both of which react to soybean seed lipoxygenase antibodies. The other two fractions contain a polypeptide of unit molecular weight reacting with the lipoxygenase antibodies.

The gene for the membrane polypeptide D2 has been mapped on the pea (Pisum sativum) chloroplast genome. The nucleotide sequence of the gene and its flanking regions is presented. The only large open reading frame in the sequence codes for a protein of MW 39.5 kD. A potential ribosome binding site is located 6 nucleotides upstream from the initiation codon and there are two sets of putative promotor sequences in the 5' flanking region. The polypeptide has a high content of hydrophobic amino acids, predominatly grouped in clusters of 20 or more residues. The 3' end of the D2 gene is overlapped by 50 nucleotides of a second open reading frame (UORF I) which is at least 369 nucleotides long. Based on current data we suggest the D2 polypeptide to be a constituent of photosystem II (PSII).

Ferredoxin-NADP+ reductase from the microalga Bumilleriopsis was isolated by a combination of affinity chromatography on a flavodoxin-Sepharose 4 B column and usual purification procedures. Both the elution pattern of the final gel filtration step and of the sodium dodecylsulfate (SDS) disc gel electrophoresis indicate that there are at least two different molecular-weight forms of the reductase, a monomeric form and a dimeric one.

Data regarding the role of oxygen in nitrite reduction are presented. In an NADPH-generating system including homogeneously purified ferredoxin-NADP reductase, ferredoxin (or flavodoxin) and nitrite reductase from the alga Bumilleriopsis filiformis, oxygen and nitrite can be reduced simultaneously. In air, rates of 1.2 mumol nitrite reduced-min-1-mg-1 nitrite reductase are obtained, which are physiologically feasible. Ferredoxin is inhibited non-competitively by oxygen during nitrite reduction. Oxygen uptake due to the oxidase reaction of ferredoxin-NADP reductase mediated by flavodoxin from Chlorella fusca and ferredoxin from Bumilleriopsis involves superoxide and is inhibited by the nitrite reducing system.

Isolated chloroplasts from Pisum sativum were found to contain at least 32 tRNA species. Hybridization of in vitro labeled, identified, chloroplast tRNAs to Pisum chloroplast DNA fragments revealed the locations of the tRNA genes on the circular chloroplast genome. Comparison of this gene map to the maps of Vicia faba and Phaseolus vulgaris showed that the chloroplast genomes of Pisum and Phaseolus are otherwise more closely related than either genome is to the chloroplast genome of Vicia. Furthermore, the results suggest how possible recombination events could be involved in the evolution of these three closely related, but divergent, chloroplast genomes.