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V Capuano

Publications and source records attributed to V Capuano.

29 records · Page 2Linked to original sources
PubMed1991

The "anchor polypeptide" of cyanobacterial phycobilisomes. Molecular characterization of the Synechococcus sp. PCC 6301 apce gene.

In cyanobacteria, light energy is mainly harvested by the phycobiliproteins that form the phycobilisome rods, and funneled to the photosynthetic reaction centers through the core components. Among them, allophycocyanin (alpha AP, beta AP) and the so-called LCM play a major role. This report deals with the characterization of the apcE gene from Synechococcus sp. PCC 6301 which specifies the LCM. It maps upstream from the apcA gene (alpha AP). Transcriptional analyses demonstrate that the apcABC gene cluster (alpha AP, beta AP, and LC7.8) forms an operon, whereas the apcE gene behaves as a monocistronic unit. The functional organization of the apcEABC gene cluster, as well as of the apcE gene product, of Synechococcus 6301 are compared to their counterparts in three other organisms. Finally, a model is proposed for the architecture of the phycobilisome core.

Amino Acid Sequence↗
PubMed1990

Molecular characterization of the terminal energy acceptor of cyanobacterial phycobilisomes.

Cyanobacteria harvest light energy through multimolecular structures, the phycobilisomes, regularly arrayed at the surface of the photosynthetic membranes. Phycobilisomes consist of a central core from which rods radiate. A large polypeptide (LCM, 75-120 kDa) is postulated to act both as terminal energy acceptor and as a linker polypeptide that stabilizes the phycobilisome architecture. We report here the characterization of the gene (apcE) that encodes this LCM polypeptide in Calothrix sp. PCC 7601. It is located upstream from the genes encoding the major components of the phycobilisome core (allophycocyanin) and is part of the same operon. The deduced amino acid sequence shows that the N-terminal region of LCM shares homology with the other phycobiliprotein subunits and thus constitutes the chromoprotein domain. The other part of the molecule is made up of four repeated domains that are highly homologous to the N-terminal regions of the phycocyanin rod linker polypeptides. The predicted secondary structure of the different domains of the LCM is discussed in relation to the different roles and properties of this large molecule.

Amino Acid Sequence↗
PubMed1988

Genes encoding core components of the phycobilisome in the cyanobacterium Calothrix sp. strain PCC 7601: occurrence of a multigene family.

The phycobilisome is the major light-harvesting complex of cyanobacteria. It is composed of a central core from which six rods radiate. Allphycocyanin, an alpha beta oligomer (alpha AP and beta AP), is the main component of the core which also contains three other phycobiliproteins (alpha APB, beta 18.3, and L92CM) and a small linker polypeptide (L7.8C). By heterologous DNA hybridization, two EcoRI DNA fragments of 3.5 and 3.7 kilobases have been cloned from the chromatically adapting cyanobacterium Calothrix sp. strain PCC 7601. Nucleotide sequence determination has allowed the identification of five apc genes: apcA1 (alpha AP1), apcA2 (alpha AP2), apcB1 (beta AP1), apcC (L7.8C), and apcE (L92CM). Four of these genes are adjacent on the chromosome and form the apcEA1B1C gene cluster. In contrast, no genes have been found close to the apcA2 gene which is carried by the 3.5-kilobase EcoRI fragment. Transcriptional analysis and 5'-end-mapping experiments were performed. The results obtained demonstrate that the apcEA1B1C gene cluster forms an operon from which segmented transcripts originate, whereas the apcA2 gene behaves as a monocistronic unit. Qualitatively, the same transcripts were identified regardless of the light wavelengths received during cell growth. The deduced amino acid sequences of the apc gene products are very similar to their known homologs of either cyanobacterial or eucaryotic origin. It was interesting, however, that in the apcA1 and apcA2 genes, whose products correspond to alpha-type allophycocyanin subunits, nucleotide sequences were more conserved (67%) than were the deduced amino acid sequences (59%).

Amino Acid Sequence↗
PubMed1988

Isolation and molecular characterization of the gene encoding allophycocyanin B, a terminal energy acceptor in cyanobacterial phycobilisomes.

Phycobilisomes are the major constituents of the light-harvesting apparatus in both cyanobacteria and red algae and consist of a central core with radiating rods. From a genomic library of the cyanobacterium Calothrix 7601, a DNA fragment encoding allophycocyanin B, one of the two terminal energy acceptors of the core, was isolated and its nucleotide sequence was determined. Unlike all the other known genes encoding phycobiliproteins, the allophycocyanin B gene, apcD, is transcribed as a monocistronic unit. Mapping of the transcripts was performed and, in contrast to some of the Calothrix genes that encode rod components, transcription was shown to occur regardless of chromatic light received during cell growth.

Amino Acid Sequence↗
PubMed1986

Sensitivity to DNA-damaging agents and mutation induction by UV light in UV-sensitive CHO cells.

Three UV-sensitive (UVs) mutants isolated from a CHO cell line were analyzed for survival after exposure to H2O2, EMS, MMC, CCNU, X-rays and for mutation induction after UV-irradiation. The UVs mutants showed normal sensitivities to EMS and H2O2, whereas they were hypersensitive to the bifunctional alkylating agents MMC and CCNU and to hypoxic X-irradiation. Compared to parental cells, one of the UV-sensitive clones showed approximately 3- and 7-fold enhancement in the mutagenic response per unit UV dose for 6-thioguanine and ouabain resistance, respectively.

Animals↗
PubMed1986

Radiation chemical and physical mechanisms of radiosensitization of single cell systems by iothalamate.

The radiosensitizing effect of iothalamate (ITA) has been investigated in bacterial and mammalian cells in order to obtain a better understanding of the physical and radiation chemical mechanisms of sensitization displayed by the drug. In order to distinguish between the two, Escherichia coli B/r cells were irradiated with 9 MeV electrons, which allow only the radiation chemical mechanism to operate, and V79 cells with 250 KVp X-rays, which instead make possible the occurrence of both mechanisms. It has been shown that: Maximum sensitization already occurs in bacteria with 10(-2) mol dm-3 ITA (enhancement ratio (ER) 11.2 in oxygen, 2.7 in nitrogen), while in mammalian cells a concentration higher by a factor of 10 is required (ER 2.2 both in air and nitrogen). ITA sensitization is inhibited when bacteria are irradiated in growth medium instead of buffer. Such inhibition does not occur with V79 cells. Cysteine and glycerol completely cancel the sensitizing effect of ITA on bacterial cells in both gas phases. Dimethylsulphoxide (DMSO) does the same in nitrogen, while in oxygen it only reduces ITA sensitization to about 50 per cent of the level observed in control conditions. With mammalian cells, all the three scavengers do not modify significantly the enhancement produced by ITA, either in air or in nitrogen. The experimental results are consistent with both postulated mechanisms of sensitization.

Animals↗
PubMedDate not supplied

Flow cytometry and sizing for routine andrological analysis.

Flow fluorometry and Coulter type sizing analysis of sperm have been applied separately in order to improve human semen analysis. Different methods of sample preparation were evaluated and a protocol involving prestaining pepsin treatment of sperm samples is proposed for fluorometric analysis. The data obtained with fluorometry and sizing analysis result in different kinds of information: Coulter counting allows to automate sperm counting and fluorometry yields more detailed information about normozoospermia and oligozoospermia by determining the proportion of mature spermatozoa and immature germ-cells. These two methods, together with light microscopy, may help to explore the correlation of fertility and pathology of spermatozoa. The aim of these investigations is to yield the preconditions for simultaneous two-parameter analysis of DNA content and cellular size distributions.

DNA↗