Modulation of heme redox potential in the cytochrome c6 family.

Cytochrome c6A is a unique dithio-cytochrome of green algae and plants. It has a very similar core structure to that of bacterial and algal cytochromes c6 but is unable to fulfill the same function of transferring electrons from cytochrome f to photosystem I. A key feature is that its heme midpoint potential is more than 200 mV below that of cytochrome c6 despite having His and Met as axial heme-iron ligands.

Structure of cytochrome c6A, a novel dithio-cytochrome of Arabidopsis thaliana, and its reactivity with plastocyanin: implications for function.

Cytochrome c6A is a unique dithio-cytochrome present in land plants and some green algae. Its sequence and occurrence in the thylakoid lumen suggest that it is derived from cytochrome c6, which functions in photosynthetic electron transfer between the cytochrome b6f complex and photosystem I. Its known properties, however, and a strong indication that the disulfide group is not purely structural, indicate that it has a different, unidentified function.

The novel cytochrome c6 of chloroplasts: a case of evolutionary bricolage?

Cytochrome c6 has long been known as a redox carrier of the thylakoid lumen of cyanobacteria and some eukaryotic algae that can substitute for plastocyanin in electron transfer. Until recently, it was widely accepted that land plants lack a cytochrome c6. However, a homologue of the protein has now been identified in several plant species together with an additional isoform in the green alga Chlamydomonas reinhardtii.

Redox properties of Arabidopsis cytochrome c6 are independent of the loop extension specific to higher plants.

Cytochrome c6 (cytc6) from Arabidopsis differs from the cyanobacterial and algal homologues in several redox properties. It is possible that these differences might be due to the presence of a 12 amino acid residue loop extension common to higher plant cytc6 proteins. However, homology modelling suggests this is not the case.

[Scoring system for chronic open glaucoma].

Purpose: The aim of this study was to evaluate a scoring system for chronic open-angle glaucoma. We devised an empirical scoring system grading severity of the disease and correlated this with treatment.

Material: and methods: Ninety patients were evaluated on 11 parameters: 1) Family history of glaucoma: blindness (2), yes (1) no (1); 2) Age: infantile (4), juvenile (4); 3) Race: Caucasian (0), Asian (1), Afro-Caribbean (2); 4) Myopia: 0-6 diopters (1), 6-12 diopters (2),>12 diopters (3); 5) Pigment dispersion or pseudoexfoliation (1); 6) Intraocular pressure without treatment:>30 mmHg (4); 25-30 mmHg (3), 20-25 mmHg (2); 7) Corneal central thickness:<500 micro m (3),>500 micro m (0); 8) Optic disc appearance: suspect (1), pathological (4); 9) Visual field defect: early (1), moderate (3), advanced (5); 10) Vascular risk factors: yes (1), no (0); 11) Loss of eyesight in one eye due to glaucoma (4).

Solution structure of a zinc substituted eukaryotic rubredoxin from the cryptomonad alga Guillardia theta.

The rubredoxin from the cryptomonad Guillardia theta is one of the first examples of a rubredoxin encoded in a eukaryotic organism. The structure of a soluble zinc-substituted 70-residue G. theta rubredoxin lacking the membrane anchor and the thylakoid targeting sequence was determined by multidimensional heteronuclear NMR, representing the first three-dimensional (3D) structure of a eukaryotic rubredoxin.

Eukaryotically encoded and chloroplast-located rubredoxin is associated with photosystem II.

We analyzed a eukaryotically encoded rubredoxin from the cryptomonad Guillardia theta and identified additional domains at the N- and C-termini in comparison to known prokaryotic paralogous molecules. The cryptophytic N-terminal extension was shown to be a transit peptide for intracellular targeting of the protein to the plastid, whereas a C-terminal domain represents a membrane anchor. Rubredoxin was identified in all tested phototrophic eukaryotes.

Transport of proteins into cryptomonads complex plastids.

Complex plastids, found in many alga groups, are surrounded by three or four membranes. Therefore, proteins of the complex plastids, which are encoded in the cell nucleus, must cross three or four membranes during transport to the plastid. To study this process we have developed a method for isolating transport-competent two membrane-bound plastids derived from the complex plastids of the cryptophyte Guillardia theta.

Identification and characterization of a eukaryotically encoded rubredoxin in a cryptomonad alga.

We have identified an open reading frame with homology to prokaryotic rubredoxins (rds) on a nucleomorph chromosome of the cryptomonad alga Guillardia theta. cDNA analysis let us propose that the rd preprotein has an NH(2)-terminal extension that functions as a transit peptide for import into the plastid. Compared to rds found in non-photosynthetic prokaryotes or found in bacteria that exhibit an anoxigenic photosynthesis apparatus, nucleomorph rd has a COOH-terminal extension, which shows high homology exclusively to the COOH-termini of cyanobacterial rds as well as to a hypothetical rd in the Arabidopsis genome.

Chloroplast protein and centrosomal genes, a tRNA intron, and odd telomeres in an unusually compact eukaryotic genome, the cryptomonad nucleomorph.

Cells of several major algal groups are evolutionary chimeras of two radically different eukaryotic cells. Most of these "cells within cells" lost the nucleus of the former algal endosymbiont. But after hundreds of millions of years cryptomonads still retain the nucleus of their former red algal endosymbiont as a tiny relict organelle, the nucleomorph, which has three minute linear chromosomes, but their function and the nature of their ends have been unclear.

Ancient gene duplication and differential gene flow in plastid lineages: the GroEL/Cpn60 example.

Cryptomonads, small biflagellate algae, contain four different genomes. In addition to the nucleus, mitochondrion, and chloroplast is a fourth DNA-containing organelle the nucleomorph. Nucleomorphs result from the successive reduction of the nucleus of an engulfed phototrophic eukaryotic endosymbiont by a secondary eukaryotic host cell.

[Pigmented basal cell carcinoma of the eyelid. Apropos of a clinical case].

A clinico-pathologic case of a 83-year-old female patient with a deeply pigmented inferior lid tumor is reported. The histopathological study of the tumor demonstrated a pigmented basal cell carcinoma. Numerous different tumors may affect the eyelids, melanocytic or not in nature.

[Palpebral form of mixed tumor of the lacrimal gland. Apropos of a case].

The clinico-pathological findings in a 45-year-old male patient with a lacrimal gland tumor are reported. This tumor had a spontaneous course of about nine years before it was resected. The clinical presentation was unusual as the tumor appeared as a nodular well-circumscribed swelling of the lateral part of the left superior eyelid.