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金沢大学理工研究域自然システム学系, A ferredoxin was purfied from the hyperthermophilic archaeon, Pyrobaculum islandicum. EPR spectra and metal content analyses suggested that the ferredoxin molecule contained one [3Fe-4S] and one [4Fe-4S] cluster. The ferredoxin was rapidly reduced by 8-oxoglutarate: ferredoxin oxidoreductase purfied from P. islandicum, indicating that it functions physiologically as an electron sink for the redox enzymes participating in glycolytic metabolism. Furthermore, the amino acid sequence of the P. islandicum ferredoxin was compared with those of several other bacterial ferredoxins.

A ferredoxin was purified from the hyperthermophilic archaeon, Pyrobaculum islandicum. EPR spectra and metal content analyses suggested that the ferredoxin molecule contained one [3Fe-4S] and one [4Fe-4S] cluster. The ferredoxin was rapidly reduced by 2-oxoglutarate: ferredoxin oxidoreductase purified from P. islandicum, indicating that it functions physiologically as an electron sink for the redox enzymes participating in glycolytic metabolism. Furthermore, the amino acid sequence of the P. islandicum ferredoxin was compared with those of several other bacterial ferredoxins.

Cytochrome c-554 from Nitrosomonas europaea was crystallized by the batch method utilizing ammonium sulfate as the precipitant. The crystals belong to the space group, P21, with unit cell dimensions of a = 64.8 A, b = 44.7 A, c = 78.7 A, and beta = 99.0 degrees. The crystals diffracted X-rays beyond 2.5 A resolution.

Cytochrome c-552 from Nitrosomonas europaea was crystallized by the sandwiched drop, vapor diffusion method, with anmmonium sulfate as the precipitant. The crystals were found to belong to the space group P2(1)2(1)2(1), having unit cell dimensions of a = 106.1 A, b = 126.1 A, and c = 57.7 A. The crystals diffracted X-rays at greater than 3.0 A resolution.

Four different membrane-bound b-type cytochromes were found to occur in Halobacterium halobium strain L-33, and two of them, b-558 and b-562, were purified to homogeneity. Cytochrome b-558 showed absorption peaks at 414 and 526 nm in the oxidized form, and peaks at 425, 528, and 558 nm in the reduced form. Its alpha peak at 558 nm in the reduced form was asymmetric with a shoulder at around 554 nm. At liquid nitrogen temperature, the a the alpha peak was split into two peaks at 549 and 556 nm which appeared to be the alpha peaks of cytochromes c and b, respectively. The cytochrome contained 1 mol of protoheme in 28,500 g, and was composed of one molecule each of two subunits with molecular masses of 15.4 and 11.7 kDa, respectively. The heme seemed bound to the larger subunit. The cytochrome was very autoxidizable and its redox potential at pH 8.0 was -75 mV. Cytochrome b-562 showed absorption peaks at 417 and 530 nm in the oxidized form and peaks at 431, 531, and 562 nm in the reduced form. The cytochrome was composed of only one polypeptide (25 kDa) and seemed to contain one protoheme molecule per molecule.

A novel type of cytochrome c oxidase was purified to homogeneity from Pseudomonas aeruginosa which was grown aerobically. The purified oxidase contained two molecules of heme a, two atoms of copper, and one molecule of protoheme per molecule. One of the two heme a molecules in the oxidase reacted with carbon monoxide, so that the enzyme was of baa3-type. The oxidase molecule was composed of three subunits with molecular weights of 38,000, 57,000, and 82,000. Although the oxidase oxidized ferrocytochrome c-550 obtained from the bacterial cells grown aerobically, the oxidizing activity was not high. The "resting form" and the "pulsed form" of the oxidase were observed clearly with this enzyme, and the transition from the resting form to the pulsed form was accompanied by a distinct change of the enzymatic activity. The difference in the kinetics of the catalytic reactions between the two forms is discussed.

The minimal structural unit of cytochrome c oxidase purified from Thiobacillus novellus was composed of one molecule each of two subunits with molecular masses of 32 and 23 kDa, respectively, and the unit had one molecule of heme a and one atom of copper. In the presence of n-octyl-beta-D-thioglucoside, the oxidase existed as the monomeric form of the unit, while it occurred as the dimeric form of the unit in the presence of Tween 20. The monomeric form showed an active cytochrome c oxidizing activity and reduced molecular oxygen to water with ferrocytochrome c. Namely, it has been shown that the bacterial cytochrome c oxidase with one heme a molecule and one copper atom per molecule can catalyze oxidation of ferrocytochrome c with concomitant reduction of molecular oxygen to water.

The membrane fraction of the facultative alkalophilic bacterium, Bacillus YN-2000, was found to contain considerably larger amounts of two c-type cytochromes, cytochromes c-553 and c-552, when the bacterium was grown at pH 10 than when it was grown at lower pHs (pH 7-9). In particular, cytochrome c-553 was present in a much higher amount in the cells grown at pH 10 than in those grown at pH 8. Cytochromes c-553 and c-552, which are membrane-bound proteins, were purified to electrophoretically homogeneous states from Bacillus YN-2000. Cytochrome c-553 showed absorption peaks at 553, 524, and 417 nm in the reduced form, and a peak at 411 nm in the oxidized form. Its molecular weight was estimated to be 10,500 from the results of SDS-polyacrylamide gel electrophoresis. However, its molecular weight was estimated to be 127,000 by gel filtration. Therefore, it seemed to occur as an oligomer in solution. The isoelectric point of cytochrome c-553 was determined to be 3.9. Its midpoint redox potential was found to be +87 mV in the pH region from 6 to 8. Cytochrome c-553 reacted with cytochrome c oxidase of the bacterium and the reaction was greatly accelerated in the presence of poly-L-lysine. Cytochrome c-552 showed absorption peaks at 552, 521, and 416 nm in the reduced form, and a peak at 408 nm in the oxidized form. The cytochrome molecule seemed to be composed of six different subunits, with molecular masses of 40, 32, 19, 17, 14, and 12 kDa, respectively.(ABSTRACT TRUNCATED AT 250 WORDS)

Catalase was purified to an electrophoretically homogeneous state from the facultative alkalophilic bacterium, Bacillus YN-2000, and some of its properties were studied. Its molecular weight was 282,000 and its molecule was composed of four identical subunits. The enzyme contained two protoheme molecules per tetramer. The enzyme showed an absorption spectrum of typical high-spin ferric heme with a peak at 406 nm in the oxidized form and peaks at 440, 559, and 592 nm in the reduced form. In contrast to the typical catalases, the enzyme was reduced with sodium dithionite, like peroxidases. The enzyme showed an appreciable peroxidase activity in addition to high catalase activity. The amino acid composition of Bacillus YN-2000 catalase was very similar to those of catalase from Neurospora crassa and peroxidase from Halobacterium halobium. The catalase content in the soluble fraction from the bacterium was higher with the cells grown at pH 10 than with the cells grown at lower pHs (pH 7-9).

A novel aco-type cytochrome-c oxidase was highly purified from the facultative alkalophilic bacterium, Bacillus YN-2000, grown at pH 10. The enzyme contained 9.0 nmol heme a/mg protein. It contained 1.23 mol of protoheme, 1.06 mol of heme c, 2.0 g atoms of copper, 2.5 g atoms of iron, and 1.8 g atoms of magnesium per mol of heme a. The enzyme molecule seemed to be composed of two subunits with Mrs of 52,000 and 41,600. On the basis of these results, the enzyme seemed to contain one molecule each of heme a, protoheme, and heme c per minimal structural unit (Mr, 93,600). Only protoheme among the three kinds of hemes in the enzyme reacted with CO and CN-. Heme a did not react with CO; cytochrome a3 did not seem to be present in the enzyme. The enzyme oxidized 314 mol of horse ferrocytochrome c per heme a per sec at pH 6.5 and the catalytic activity was 50% inhibited by 7.65 microM KCN. The enzymatic activity was found to be optimal at pH 6.0.

Aleuria aurantia lectin (AAL) is a protein composed of two identical subunits having no carbohydrate chain and shows sugar-binding specificity for L-fucose. Full-length cDNA encoding for the lectin has been isolated from a lambda gt11 library, screened with an antiserum directed against AAL. The cDNA clone contained 1,370 nucleotides and an open reading frame of 939 nucleotides encoding 313 amino acids. The amino-terminal sequence (residues 1-30) of the lectin isolated from the mushroom coincided with the deduced amino acid sequence starting from proline at the 2nd residue, indicating that the mature AAL consists of 312 amino acids. Its molecular weight is calculated to be 33,398. The deduced amino acid sequence shows that AAL includes six internal homologous regions, and has considerable homology with a hemagglutinin from a Gram-negative bacterium, Myxococcus xanthus, which forms a fruiting body. No significant homology was observed with higher plant or animal lectins. The recombinant AAL produced by Escherichia coli JM109 carrying the AAL expression plasmid pKA-1 [Fukumori, F. et al. (1989) FEBS Lett. 250, 153-156] was purified from the cell lysate by affinity chromatography using a fucose-starch column, and hundreds of milligrams of the lectin was obtained. The recombinant lectin showed the same biochemical characteristics and sugar binding specificity as did the natural AAL.

Cytochrome c oxidase (cytochrome aa3-type) [EC 1.9.3.1] was purified from Erythrobacter longus to homogeneity as judged by polyacrylamide gel electrophoresis, and some of its properties were studied. The spectral properties of the oxidase closely resembled those of mitochondrial and other bacterial cytochromes aa3. The enzyme showed absorption peaks at 430 and 598 nm in the oxidized form, and at 444 and 603 nm in the reduced form. The CO compound of the reduced enzyme showed peaks at 432 and 600 nm. The enzyme oxidized eukaryotic ferrocytochromes C more rapidly than E. longus ferrocytochrome c. The reactions catalyzed by the enzyme were 50% inhibited by 0.7 microM KCN. The enzyme contained 1 g atom of copper and 1 g atom of magnesium per mol of heme a. The enzyme molecule seemed to be composed of two identical subunits, each with a molecular weight of 43,000.

Cytochrome c oxidase (cytochrome aa3-type) [EC 1.9.3.1] was purified from Nitrobacter agilis to an electrophoretically homogeneous state and some of its properties were studied. The enzyme showed absorption peaks at 422, 598, and 840 nm in the oxidized form, and at 442 and 606 nm in the reduced form. The CO compound of the reduced enzyme showed peaks at 436 and 604 nm, and the latter peak had a shoulder at 599 nm. The enzyme possessed 1 mol of heme a and 1.6 g-atom of copper per 41,000 g, and was composed of two kinds of subunits of 51,000 and 31,000 daltons. These results show that the structurally minimal unit of the enzyme molecule is composed of one molecule each of the two subunits and contains 2 molecules of heme a and 2-3 atoms of copper. the enzyme rapidly oxidized ferrocytochromes c of several eukaryotes as well as N. agilis ferrocytochrome c-552. The reactions catalyzed by the enzyme were strongly inhibited by KCN. The reduction product of oxygen catalyzed by the enzyme was concluded to be water on the basis of the ratio of ferrocytochrome c oxidized to molecular oxygen consumed.

From Pseudomonas AM 1 grown in a medium deficient in Cu, aa3-type cytochrome c oxidase was purified which contained 2 molecules of haem a and one atom of Cu per molecule. The enzyme showed absorption peaks at 428 and 595 nm in the oxidized form and at 442 and 604 nm in the reduced form, and its CO complex showed peaks at 432 and 602 nm. The enzyme in the oxidized state showed an obscure absorption peak around 800 nm instead of a peak at 820 nm. One mol of the enzyme oxidized maximally 76, 75, and 98 mol of the ferrocytochromes c of Candida krusei, horse and Pseudomonas AM 1 per sec, respectively. These reactions were 50% inhibited by 7 microM KCN. The product of reduction of O2 catalyzed by the enzyme was concluded to be H2O on the basis of the ratio of ferrocytochrome c oxidized to O2 consumed.

The function and the structural features of Chromatium vinosum cytochrome c-552 have been investigated. Cytochrome c-552 has a sulfide-cytochrome c reductase activity and also catalyzes the reduction of elementary sulfur to sulfide with reduced benzylviologen as the electron donor. In the sulfide-cytochrome reduction, horse and yeast cytochromes c act as good electron acceptors, but cytochrome c' or cytochrome c-553(550) purified from the organism does not. The subunit structure of cytochrome c-552 has been studied. The cytochrome is split by 6 M urea into cytochrome and flavoprotein moieties with molecular weights of 21,000 and 46,000, respectively. The flavoprotein moiety is obtained by isoelectric focusing in the presence of 6 M urea and 0.1% beta-mercaptoethanol, while the hemoprotein moiety is obtained by gel filtration with Sephacryl S-200 in the presence of 6 M urea and 0.1 M KCl. Neither subunit has sulfide-cytochrome c reductase activity. Attempts to reconstitute the original flavocytochrome c from the subunits have been unsuccessful.

Cytochrome c oxidase (cytochrome aa3-type) [EC 1.9.3.1] was purified from Pseudomonas AM 1 to an electrophoretically homogeneous state and some of its properties were studied. The oxidase showed absorption peaks at 428 and 598 nm in the oxidized form, and at 442 and 604 nm in the reduced form. The CO compound of the reduced enzyme showed peaks at 432 and 602 nm. The enzyme molecule was composed of two kinds of subunits with molecular weights of 50,000 and 30,000 and it contained equimolar amounts of heme a and copper atom. The enzyme rapidly oxidized Candida krusei and horse ferrocytochromes c as well as Pseudomonas AM 1 ferrocytochrome c. The reactions catalyzed by the enzyme were strongly inhibited by KCN.

The electron transport system coupled to the oxidation of methylamine in Pseudomonas AM1 was investigated by reconstituting it from the highly purified components. A mixture of methylamine dehydrogenase, cytochrome cH and cytochrome c oxidase (= cytochrome aa3) actively oxidized methylamine (161 mol of O2 consumed/mol of heme a of cytochrome c oxidase X min). In this system, addition of amicyanin did not affect the oxygen consumption rate. The oxygen consumption rate of the cell-free extract prepared from the cells cultivated in a copper-deficient medium was directly proportional to the amount of amicyanin added, and extrapolation to zero copper concentration gave a value of 28 mol of O2 consumed/mol of heme a of cytochrome c oxidase X min. These results suggest that methylamine oxidation in the bacterium can occur at least to some extent without participation of amicyanin.

An a-type cytochrome was purified from Halobacterium halobium. The cytochrome showed an absorption spectrum similar to that of cytochrome aa3; it showed absorption peaks at 420 and 598 nm in the resting state, peaks at 441 and 602 nm in the reduced form, and its CO compound showed peaks at 430 and 600 nm. The cytochrome molecule was composed of only one kind of polypeptide with the molecular weight of 40,000. The cytochrome contained two heme a molecules in the molecule but no copper. The cytochrome did not show cytochrome c oxidase activity. Midpoint redox potential at pH 8.0 of the cytochrome was determined to be +0.31 V. The amino acid composition of the cytochrome resembled that of subunit I of mitochondrial cytochrome aa3. While two molecules of heme a were reduced with sodium dithionite, only one of two heme a molecules was reduced with ascorbate plus TMPD. The heme a reduced with ascorbate plus TMPD did not react with molecular oxygen or carbon monoxide, while one of two heme a molecules reduced with sodium dithionite was oxidized by molecular oxygen and combined with carbon monoxide.

Proteoliposomes reconstituted from purified cytochrome c oxidase of Pseudomonas AM1 and from a heptyl beta-D-thioglucoside-extract of its membranes showed respiratory control but did not show H+ pumping upon a pulse with reduced cytochrome c. The stoichiometries of respiration-dependent H+ translocation in the resting cells respiring ascorbate via N,N,N',N'-tetramethyl-p-phenylenediamine were measured by the oxygen-pulse and initial rate methods. The apparent H+/O ratio of about 2 was due to 2H+ release from the hydrogen-donating substrate. These results strongly suggested that Pseudomonas AM1 does not pump H+ intrinsically, although the enzyme catalyzes electron transfer across the membranes.

Cytochrome a1c1 (nitrite-cytochrome c oxidoreductase) purified from Nitrobacter winogradskyi (formerly N. agilis) contained molybdenum, non-heme iron, and acid-labile sulfur in addition to hemes a and c; it contained 1 mol of heme a, 4-5 g atoms of non-heme iron, 2-5 g atoms of acid-labile sulfur, and 1-2 g atoms of molybdenum per mol of heme c, but did not contain copper. The fluorescence spectra of the molybdenum cofactor derivative prepared from cytochrome a1c1 were very similar to those of the cofactor derivative from xanthine oxidase, and the aponitrate reductase of nit-1 mutant of Neurospora crassa was complemented by addition of the molybdenum cofactor derived from the cytochrome. Further, the ESR spectrum of cytochrome a1c1 was similar to that of liver sulfite oxidase. The content of cytochrome a1 in the cells cultivated with the medium in which tungsten was substituted for molybdenum markedly decreased as compared with that in the cells cultivated in the molybdenum-supplemented medium. These results indicate that cytochrome a1c1 is an iron-sulfur molybdoenzyme which contains hemes a and c.

A peroxidase was purified from Halobacterium halobium L-33 to an electrophoretically homogeneous state and some of its properties were studied. The enzyme showed an absorption peak at 406 nm in the oxidized form and peaks at 440, 558, and 591 nm in the reduced form. The difference spectrum, reduced + CO minus reduced, of the enzyme showed peaks at 425, 538, and 577 nm and troughs at 444, 562, and 596 nm. These spectral properties were apparently similar to those of "cytochrome a1" except for the occurrence of the peak at 558 nm in the reduced form. The molecular weight of the enzyme was 110,000 and the enzyme possessed one unit of protoheme in the molecule. The activity to oxidize guaiacol in the presence of H2O2 of the peroxidase was about one-twentieth of that of horseradish peroxidase. The enzyme also showed a catalase-activity one-fourth as active as that of liver catalase. The reactions catalyzed by the enzyme were strongly inhibited by KCN.