Oxidation of diaminobenzidine in the heterocysts ofAnabaena cylindrica

Murry, Marcia A.; Olafsen, Astrid G.; Benemann, John R.

doi:10.1007/bf01566972

Cited by 31 publications

(26 citation statements)

References 21 publications

Supporting

Mentioning

Contrasting

Order By: Relevance

“…Cyanoglobin does oxidize 3,3Ј-diaminobenzidine (55), and it is also a hemoprotein which accumulates in the cell wall of heterocysts. However, the conditions under which cyanoglobin is synthesized, as well as the apparent lack of sequences which are homologous to glbN in a number of Nostoc and Anabaena spp., seem to exclude a general function for GlbN in the 3,3Ј-diaminobenzidine staining of the honeycomb region of heterocysts (10,33,39).…”

Section: Discussionmentioning

confidence: 92%

“…Third, hemoproteins, such as FixL (an oxygen-sensor and kinase) in R. meliloti, may have regulatory functions in nitrogen fixation (15). Specifically, for cyanobacteria, it has been suggested that hemoproteins in the cell wall and in the honeycomb membrane system of the heterocyst play a part in the binding of oxygen or protection of the nitrogenase complex (39). The subcellular location of these proteins in heterocysts was determined by their ability to oxidize 3,3Ј-diaminobenzidine in the dark.…”

Section: Discussionmentioning

confidence: 99%

“…Certain of the modifications that arise during the differentiation of the cyanobacterial heterocyst may alleviate the effects of potentially toxic oxygen concentrations. These modifications include the loss of photosystem II function (19), the formation of a diffusion barrier with a reduced permeability to gases including oxygen (29,40), attenuation of oxygen tension through the coupling of diffusion-limited kinetics and respiratory electron transport (39), and modification of nitrogenase to an O 2 -insensitive form (51). The maturation of heterocysts can be blocked when mutations are introduced in genes that contribute to the developmental pathway (5,58).…”

mentioning

confidence: 99%

See 2 more Smart Citations

GlbN (cyanoglobin) is a peripheral membrane protein that is restricted to certain Nostoc spp

et al. 1996

View full text Add to dashboard Cite

The glbN gene of Nostoc commune UTEX 584 is juxtaposed to nifU and nifH, and it encodes a 12-kDa monomeric hemoglobin that binds oxygen with high affinity. In N. commune UTEX 584, maximum accumulation of GlbN occurred in both the heterocysts and vegetative cells of nitrogen-fixing cultures when the rate of oxygen evolution was repressed to less than 25 mol of O 2 mg of chlorophyll a ؊1 h ؊1 . Accumulation of GlbN coincided with maximum synthesis of NifH and ferredoxin NADP ؉ oxidoreductase (PetH or FNR). A total of 41 strains of cyanobacteria, including 40 nitrogen fixers and representing 16 genera within all five sections of the cyanobacteria were screened for the presence of glbN or GlbN. glbN was present in five Nostoc strains in a single copy. Genomic DNAs from 11 other Nostoc and Anabaena strains, including Anabaena sp. strain PCC 7120, provided no hybridization signals with a glbN probe. A constitutively expressed, 18-kDa protein which cross-reacted strongly with GlbN antibodies was detected in four Anabaena and Nostoc strains and in Trichodesmium thiebautii. The nifU-nifH intergenic region of Nostoc sp. strain MUN 8820 was sequenced (1,229 bp) and was approximately 95% identical to the equivalent region in N. commune UTEX 584. Each strand of the DNA from the nifU-nifH intergenic regions of both strains has the potential to fold into secondary structures in which more than 50% of the bases are internally paired. Mobility shift assays confirmed that NtcA (BifA) bound a site in the nifU-glbN intergenic region of N. commune UTEX 584 approximately 100 bases upstream from the translation initiation site of glbN. This site showed extensive sequence similarity with the promoter region of glnA from Synechococcus sp. strain PCC 7942. In vivo, GlbN had a specific and prominent subcellular location around the periphery of the cytosolic face of the cell membrane, and the protein was found solely in the soluble fraction of cell extracts. Our hypothesis is that GlbN scavenges oxygen for and is a component of a membrane-associated microaerobically induced terminal cytochrome oxidase.

show abstract

Section: Discussionmentioning

confidence: 92%

Section: Discussionmentioning

confidence: 99%

mentioning

confidence: 99%

See 1 more Smart Citation

GlbN (cyanoglobin) is a peripheral membrane protein that is restricted to certain Nostoc spp

et al. 1996

View full text Add to dashboard Cite

show abstract

“…Recent studies (5) by immunocytochemistry detected nitrogenase only in the central cytoplasm and not in the polar regions. Because other authors (18) revealed, by light-independent DAB oxidation, the presence of hemeproteins in the honeycomb region and at the periphery of heterocysts, the question arises, could Fe-SOD be localized in the honeycomb regions? Immunocytochemical experiments are in progress in order to answer this question.…”

Section: Discussionmentioning

confidence: 99%

“…Moreover, hydrogen peroxide was detected in the honeycomb region by DAB-oxydation (18), suggesting the presence in heterocysts of partially reduced molecular oxygen.…”

mentioning

confidence: 98%

Superoxide Dismutase in the Symbiont Anabaena azollae Strasb.

Canini¹,

Galiazzo²,

Rotilio³

et al. 1991

Plant Physiol.

View full text Add to dashboard Cite

Superoxide dismutase was investigated in the symbiont Anabaena azollae Strasb. living in Azolla filiculoides Lam. In vegetative cells, three isoenzymatic forms of superoxide dismutase, containing manganese, iron, and the hybrid iron-manganese, respectively, were present. Hybrid superoxide dismutase, detected for the first time in cyanobacteria, was 7% of the total superoxide dismutase present in vegetative cells. All three superoxide dismutase forms increased in the Anabaena vegetative cells obtained from irradiated plants grown in winter. In heterocysts, only an iron superoxide dismutase was present, which amounted to 25% of total vegetative cell superoxide dismutase activity. Hybrid superoxide dismutase appeared in heterocysts after irradiation. In vegetative cells of Anabaena from plants grown in summer, the basal level of total superoxide dismutase increased by 60% as compared with winter, and was unaffected by irradiation. The levels of superoxide dismutase in heterocysts from control and exposed plants grown in summer were comparable to those observed in heterocysts obtained from the plants grown during winter. No direct correlation was found between nitrogenase activity and superoxide dismutase in heterocysts. The presence of cyanophycin granules, either within the heterocyst pore channel or close to the transversal septum of vegetative cells, suggested a mechanism to stop communications between vegetative cells and heterocysts.

show abstract