Contribution to the structural characterization of eucaryotic PSI reaction centre—I. Critical analysis of the polypeptidic composition of different P700 enriched fractions

In thylakoid membranes, several peptides of high MW are present which may interfere with the study of CP1's components. Modifying Cleveland's technique [7] for limited proteolysis, we have characterized the polypeptides found in the 60 kD region. Some may result from incomplete washing of the CF1 while others come from the CP1; indeed, this chlorophyll protein complex, which has a higher MW (above 100 kD), very often undergoes a dissociation into smaller components of about 60 KD MW.Analysis of the protein content of different preparations commonly used to obtain PSI reaction centre enriched fractions has been performed. The and subunits of CF1 are among the main contaminants of most of these preparations. A further purification step is described which can be applied to all these preparations, but numerous peptides are still present in the active fractions. It is most unlikely that all these polypeptides are required for the primary photochemical event, and this emphasizes the necessity to find a new simple method to purify PSI reaction centres.     

Contribution to the structural characterization of eucaryotic PSI reaction centre — II. Characterization of a highly purified photoactive SDS-CP1 complex

Under precise conditions, SDS PAGE allows purification of a photoactive P700-chla-protein complex from eucaryotic cells. The yield of P700 recovery is close to 100%. A total protein content equivalent to about 140 kD for one mole of P700 has been estimated by chemical analysis, and electrophoresis revealed the presence of two peptidic chains with MWs close to 65 kD. Photochemical and structural properties of this complex are given and compared with those of other complexes previously isolated.     

Sodium and potassium interactions with Na+-ATPase of inside-out membrane vesicles from high-K+ and low-K+ sheep red cells

Na⁺-ATPase of high-K⁺ and low-K⁺ sheep red cells was examined with respect to the sidedness of Na⁺ and K⁺ effects, using inside-out membrane vesicles and very low ATP concentrations (?2 μM). With varying amounts of Na⁺ in the medium, i.e., at the cytoplasmic surface, Na_cyt⁺, the activation curves show that high-K⁺ Na⁺-ATPase has a higher affinity for Na_cyt⁺ compared to low-K⁺. The apparent affinity for Na_cyt⁺ is also increased by increasing the ATP concentrations in high-K⁺ but not low-K⁺. With Na_cyt⁺ present, Na⁺-ATPase is stimulated by intravesicular Na⁺, i.e., Na⁺ at the originally external surface, Na_ext⁺, to a greater extent in low-K⁺ than high-K⁺. Intravesicular K⁺ (K_ext⁺) activates Na⁺-ATPase in high-K⁺ but not in low-K⁺ vesicles and extravesicular K⁺ (K_cyt⁺) inhibits low-K⁺ but not high-K⁺ Na⁺-ATPase. Thus, the genetic difference between high-K⁺ and low-K⁺ is expressed as differences in apparent affinities for both Na⁺ and K⁺ and these differences are evident at both cytoplasmic and external membrane surfaces.     

Sialyl-transferase mitochondriale

A sialyl transferase activity is found in purified mitochondria. It is not due to residual contamination and this enzymatic system is located in the outer mitochondrial membrane. This proves mitochondrial autonomy in regard to glycoconjugate sialylation.     

Micrococcus luteus endonucleases for apurinic/apyrimidinic sites in deoxyribonucleic acid. 2. Further studies on the substrate specificity and mechanism of action

Two endonucleases specific for DNA-containing apurinic or apyrimidinic sites (AP-endonucleases A and B) have been isolated from Micrococcus luteus and highly purified. These enzymes have no exonuclease activity. Both AP-endonucleases hydrolyze DNA-containing apurinic or apyrimidinic sites at the 5' end of the lesion, thus generating 3'-hydroxyl and 5'-phosphoryl end groups. DNA-containing pyrimidine dimers, introduced at low doses of UV, are not hydrolyzed, whereas DNA-containing lesions, introduced at high doses of UV or by gamma irradiation are nicked by either AP-endonuclease. During hydrolysis of apurinic DNA, neither of the AP-endonucleases acts as a processive enzyme.     

Use of RP4-prime plasmids constructed in vitro to promote a polarized transfer of the chromosome in Escherichia coli and Rhizobium meliloti.

Summary RP4-prime plasmids containing chromosomal fragments of either Escherichia coli or Rhizobium meliloti were constructed in vitro. When introduced into E. coli or R. meliloti respectively, they promoted a polarized transfer of the chromosome as demonstrated either by the gradient of transfer of various markers or by the study of the genetic constitution of recombinants. In E. coli, mobilization was shown to be dependent upon the presence of a functional rec A system. Inheritance of markers was due to their integration into the chromosome of the recipient as shown by the need for a functional rec A system in the recipient E. coli or by mobilization of recessive markers in R. meliloti. The system described could be applied to genetic mapping in any Gram negative bacteria.     

Search for a relationship between molecular anomalies of the mutant erythrocyte pyruvate kinase variants and their pathological expression

Summary Anomalies of the mutant pyruvate kinase variants and clinical symptoms have been compared in 22 unrelated patients with congenital red cell pyruvate kinase deficiency. This study suggests that some characteristics of the mutant enzymes could play a role in the intensity of haemolysis, namely residual activity, affinity for the substrate phosphoenolpyruvate and for the allosteric activator fructose 1,6 diphosphate and inhibition by ATP.     

A functional evenness index for microbial ecology

Microbial ecologists attempting to describe community structures through the use of synthetic parameters face enormous difficulties. These stem in part from the necessity of using standard taxonomic reference levels in a field where the species level is poorly defined. This paper presents an attempt to obviate this problem. A “functional evenness” index (E) is defined using information measures; it is based directly on the characteristics of the bacteria, as determined, for example, with the API 20B method. Comparisons of this index with classic structure indices, such as taxonomic evenness (Pielou) or systematic dominance (Hulburt), show that it behaves like an evenness index, while bypassing the taxonomic study required before computation of the classic indices. Its use is illustrated with samples of aerobic heterotrophic bacteria obtained from brackish lagoon sediments. We are grateful to our statistician colleagues, Dr. Yves Lepage from Université de Montréal and Dr. André Plante from Université du Québec à Montréal. Both have contributed important elements to the discussion presented in this Appendix.     

The HLA-D system: At least two loci and four distinct phenotypic traits per haplotype. Introduction to component typing in families and population by primed lymphocyte typing

Using a number of intrafamilial PLTs raised against identical HLA haplotypes it has been possible to construct a model in an informative family defining the HLA-D region as a genetic system. This system consists of at least two regions separated by a recombination between HLA-D and GLO. In relation to the site of recombination, a minimum of one centromeric and three telomeric components can be identified per haplotype.—Fourteen PLTs raised and defined within the family were subsequently tested in a Caucasian population (n=84) and in 13 unrelated, complete families.—It is concluded that the hypothetical model proposed for the HLA-D region as a genetic system of linked loci, coding at the cell surface for associated but distinct components (at least four per haplotype), allows for typing of the components of the HLA-D system of any given haplotype. Serological typing of HLA-D components should, in the near future, provide a more convenient way of establishing component phenotypes than the present use of primed lymphocyte typing reagents. Among the components isolated, some have a high association with the classic alleles defined either by homozygous typing cells or DR serology. Others form the basis of cross-reactivity but their presence does not interfere with standard typing. Others, however, seem by their mere presence to be responsible for false assignments.—The concept of HLA-D as a genetic system clarifies many of the inconsistencies observed with a one-locus system.Research scientists from INSERM.Research Fellow from the Danish Medical Research Council.Central Blood Bank — Marseille