The molar extinction coefficient for phycoerythrobilin (l a) was calculated by two independent methods. It is different from that of the cleaved chromophore, phycobiliviolin (2). By unfolding with urea or tryptic digestion, the chromophore absorption of C-phycoerythrin (PE) was determined free of any protein influence. The chromophore content of PE from various Cyanobacteria was determined with these data to be either 5 or 6, depending on the organism. This corresponds to a chromophore distribution over phycoerythrin subunits alpha:beta of either 2:3 or 2:4. The phylogenetic significance of varying chromophore content is discussed.

Cyanobacteria↗

PubMedDate not supplied

Partial proteolysis of rice phytochrome: comparison with oat phytochrome.

Phytochrome was isolated from etiolated rice seedlings (Oryza sativa L.) by slight modification of the procedure for oat phytochrome. Spectral data of rice phytochrome are comparable with those of oat and rye phytochrome. Controlled proteolysis with endoproteinases Lys-C and Glu-C yielded defined fragments some of which were different for Pr and Pfr. The fragments were identified by comparison with the corresponding fragments of oat phytochrome and by comparison of the amino acid sequences of rice and oat phytochrome. Regions of the peptide chain which are differently exposed in Pr and Pfr were identified. A highly conserved sequence around residues 740-750 is discussed as candidate for an "active center" of signal transduction.

Amino Acid Sequence↗

PubMedDate not supplied

Natural inhibitors of germination and growth, VII synthesis of ribulosebisphosphate carboxylase in darkness and its inhibition by coumarin.

Cress (Lepidium sativum) seeds were germinated in darkness. Seedlings were investigated for soluble proteins by SDS-PAGE. Two proteins were identified by microsequencing: the small subunit of ribulosebisphosphate carboxylase (SSU) and the alpha subunit of the storage protein cruciferin. Net synthesis of small and large subunits of ribulosebisphosphate carboxylase (SSU and LSU) was investigated by Western blot. Net synthesis of both subunits was inhibited by coumarin. To the contrary, net synthesis of cruciferin was increased by coumarin. With specific cDNA probes, we determined steady state levels of the corresponding mRNAs (rbcS mRNA for SSU, rbcL mRNA for LSU). Both mRNAs can be detected in dry seeds; their amount increases during germination in the dark. Incubation with coumarin inhibits this increase. Inhibition of development by coumarin on the level of transcription is discussed.

Amino Acid Sequence↗

PubMedDate not supplied

On the expression of several Lhc genes in garden cress (Lepidium sativum L.).

The polymerase chain reaction was used to prepare gene-specific probes for several Lhc genes coding for chlorophyll a/b-binding proteins of cress (Lepidium sativum L.). Due to the presence of about 150 basepairs of the coding region, the isolated clones could be attributed to Lhc a3 (1 clone), Lhc b1 (5 clones), Lhc b2 (1 clone) and Lhc b3 (1 clone) genes. Probes prepared from the 3'non-coding regions of the clones did not cross-hybridize; they were specific for 3 different Lhc b1 transcripts and one each of Lhc b2, Lhc b3 and Lhc a3 transcripts. The transcript levels were higher in leaves than in cotyledons of light-grown seedlings; they decreased significantly in cotyledons from week 1 to week 4. The levels of 2 Lhc b1 transcripts (detected with probes cd1 and cd2) changed from 1 week old cotyledons (30% cd1, 28% cd2) to 3 months old leaves (14% cd1), 44% cd2), stems (11% cd1, 56% cd2) and fruits (15% cd1, 62% cd2, all values percent of total transcripts), whereas transcript levels of another Lhc b1 gene (detected with probe cd3) and of a Lhc a3 gene remained nearly constant. The level of Lhc b2 and Lhc b3 transcripts were 1-2 orders of magnitude smaller than those of the other Lhc transcripts. The data obtained with cress plants are compared with published data from other plants.

Amino Acid Sequence↗