Preliminary X-ray diffraction studies on a ferredoxin from the thermophilic archaebacterium,Thermoplasma acidophilum

A ferredoxin from the thermophilic archaebacterium, Thermoplasmaacidophilum, is supposed to contain two (4Fe-4S) active centers; one center could be linked by four cysteine residues to the protein and the other bonded with three cysteines and an unknown group. This ferredoxin has been crystallized by salting-out against 2.3 m-ammonium sulfate solution. The space group is P2₁2₁2 with cell dimensions of $\text{a = 59.20}\text{A}\text{?}\text{, b = 52.77}\text{A}\text{?}\text{and}\text{c = 41.28}\text{A}\text{?}$. Four molecules pack in the unit cell with $\text{V}{}_{\mathrm{<mtext>m</mtext>}}\text{= 2.03}\text{A}\text{?}{}^3\text{/dalton}$.     

A Comparative Study of the Biological Activities of Two Molecular Species of Chloroplast-type Ferredoxins

Pairs of two molecular species of soluble chloroplast-type ferredoxins(Fd I and Fd II) from Nostoc muscorum and Aphanothece sacrumwere used to examine and compare the abilities of ferredoxinto substitute for spinach ferredoxin in the photoreduction ofNADP⁺ by spinach chloroplasts or N. muscorum membrane fragmentsand to link the reducing power of illuminated spinach chloroplaststo the Bacillus polymyxa nitrogenase system. Ferredoxins II of Nostoc and Aphanothece showed rather low activitiesin NADP⁺ photoreduction and nitrogenase system with spinachchloroplasts as the photosensitizer, compared to other ferredoxins.However, there was no difference between two ferredoxins (FdI and Fd II) from Nostoc in NADP⁺ photoreduction by photosyntheticmembrane fragments prepared from the same organism, N. muscorum. The biological significance of two molecular species of ferredoxinsin one organism could be ascribed to the different contributionof each ferredoxin to certain biological reactions in whichferredoxin functioned as an electron carrier. (Received November 4, 1980; Accepted January 9, 1981)     

Photochemical activity and components of membrane preparations from blue-green algae. I. Coexistence of two photosystems in relation to chlorophyll a and removal of phycocyanin

Nostoc muscorum (Strain 7119) cells were disrupted and the accessory pigment phycocyanin was removed from membrane fragments by digitonin treatment. The phycocyanin-depleted membrane fragments retained both Photosystem I and Photosystem II activity, as evidenced by high rates of NADP⁺ photoreduction either by water or by reduced 2,6-dichlorophenolindophenol, indicating that phycocyanin is not an essential component for electron transport activity.No separation of the two photosystems was effected by the digitonin treatment. Even drastic digitonin treatments failed to diminish significantly the remarkably stable electron transport from water to NADP⁺.Action spectra and relative quantum efficiency measurements demonstrated the existence of both Photosystem I and Photosystem II in membrane fragments which contained chlorophyll a as the only significant light-absorbing pigment.     

Ferredoxin Isolated from Plant Non-Photosynthetic Tissues. Purficaition and Characterization

A ferredoxin was isolated from non-photosynthetic tissues ofthe lower storage root of radish (Raphanus sativus L. var. acantiformiscultivar Miyashige) in a pure form by conventional means. Itshowed the characteristic features in its absorption spectrumof chloroplast-type ferredoxin. However, amino acid compositionand amino (N)- terminal sequence were different from those ofradish leaf ferredoxin. Root ferredoxin was able to transferelectrons from dithionite to nitrite reductase [EC 1.7.7.1 [EC] ]isolated from mung bean seedling roots and also to mediate NADP⁺photoreduction in spinach broken chloroplasts. It therefore is suggested that a set of distinctive molecularspecies of ferredoxin is present in non-photosynthetic tissuesand functions as a redox mediator in ferredox-independent enzymesystems. (Received October 18, 1985; Accepted January 16, 1986)     

The Isolation and Characterization of a Cytochrome b6f Complex from the Cyanobacterium Spirulina sp.

A cytochrome b₆f complex was isolated and purified from Spirulinasp. The complex was solubilized with n-heptyl ß-D-thioglucosideand chromatographed on a DEAE-Toyopearl 650M column. The purifiedcomplex contained a small amount of chlorophyll and carotenoid.At least four polypeptides were present in the complex: cytochromef (29 kDa), cytochrome b₆(23 kDa), iron-sulfur protein (ISP,23 kDa), and a 17 kDa polypeptide. Each polypeptide was separatedfrom the complex treated with 2-mercaptoethanol or urea. Theabsorption spectra of cytochrome b₆ and cytochrome f were similarto those of Anabaena and spinach as expected. The complex wasactive in supporting ubiquinol-cytochrome c oxidoreductase activity.Fifty percent inhibition of the activity was accomplished by1 µM dibromothymoquinone (DBMIB). The K_m values for ubiquinol-2and cytochrome c (horse heart) were 5.7 µM and 7.4 µM,respectively. (Received August 15, 1988; Accepted November 14, 1988)     

A new aging technique by UV light observation of burnt otoliths for the conger eel Conger myriaster (Brevoort)

A new aging method, fluorescent observation of burnt otoliths, was discovered to disclose the age and growth of the conger eel. Under UV light, bright fluorescent zones were visible in the burnt otolith but not in the unburnt otolith. An illumination wavelength around 380 nm was found to be suitable for fluorescence observation of burnt otoliths. Bright zones of the conger eel otolith formed around June–August in Sendai Bay and were validated as annuli. The conger eels caught by net pot fishery were found to be mainly aged from 1+ to 4+ years. Received: March 7, 2001 / Revised: September 12, 2001 / Accepted: October 10, 2001     

Involvement of Carboxyl Groups of the PSII Reaction Center Proteins in Photoactivation of the Apo-Water-Oxidizing Complex

Involvement of residues of acidic amino acids in photo-ligationof manganese into the apo-water-oxidizing complex was investigatedby use of l-ethyl-3-[3-(dimethylami-no)propyl]carbodiimide (EDC),a water-soluble carboxyl modifier. Treatment of Mn-depletedPSII membranes by EDC in the presence of nucleophiles induceda loss of photoactivation capability in the Mn complex and partialloss of capability of photooxidation of Mn²⁺, but little decreasein the DCIP photoreduction supported by diphen-ylcarbazide.The inhibition of diphenylcarbazide-photo-oxidation by submicromolarMn²⁺, indicative of the intactness of high-affinity Mn-bindingsites, was apparently abolished by EDC treatment. From aminoacid quantitation analysis of Dl and D2 proteins and CP47 ofthe chemically-modified membranes, approximately three carboxylgroups of the D1 protein were found to be chemically-modifiedwith EDC after removal of the functional Mn. These results suggestthat acidic amino acids on the D1 protein are involved in photoactivationof the apo-water-oxidizing complex and probably in ligationof Mn to the water-oxidizing complex. (Received October 21, 1996; Accepted March 3, 1997)     

Cytocbromec-554 derived from the blue-green alga Spirulina platensis

Cytochrome c-554 was purified from Spirulina platensis and someof its properties were studied. The cytochrome shows absorptionpeaks at 354, 410 and 529 nm in the oxidized form and at 318,416, 523 and 553.6 nm in the reduced form. The a peak at 553.6nm is slightly asymmetric with a shoulder around 550 nm. Theisoelectric point, midpoint redox potential and molecular weightof the cytochrome are 4.9, +0.35 V and 10,000, respectively.The cytochrome reacts fairly rapidly with Pseudomonas aeruginosanitrite reductase but does not react with cow cytochrome oxidase.The reactivities with the two enzymes of the S. platensis cytochromehave been compared with those of other algal c-type cytochromes. (Received August 22, 1977; )