A protease from rat intestine

Partially purified ribonuclease H from rat liver nuclei can be inactivated by a soluble fraction from rat intestine; this inactivation is restored by adding trypsin inhibitor, suggesting that the factor is a protease. A preparation has been isolated and purified to homogeneity. The molecular weight of the enzyme was estimated as 28 000 with an optimum pH of 8.0 and an isoelectric point at pH 4.5--4.7. The inactivating and proteolytic activities were observed in parallel throughout the purification procedures. Diisopropylphosphorofluoridate inhibited the protease activity. The protease inactivates deoxyribonuclease I, pyruvate kinase, and aldolase. From experiments with protease modifiers, it seems to be a serine protease of a trypsin-like nature.

Amino acid sequence of a purothionin homolog from barley flour

A purothionin homolog was isolated from barley flour and purified by CM-52 column chromatography. It showed potent lethal activity towards brewer's yeast and its complete amino acid sequence was determined to be as follows. Lys-Ser-Cys-Cys-Arg-Ser-Thr-Leu-Gly-Arg-Asn-Cys-Tyr-Asn-Leu-Cys-Arg-Val-Arg-Gly-Ala-Gln-Lys-Leu-Cys-Ala-Gly-Val-Cys-Arg-Cys-Lys-Leu-Thr-Ser-Ser-Gly-Lys-Cys-Pro-Thr-Gly-Phe-Pro-Lys. It thus consists of 45 amino acid residues with 8 cysteines. The number of amino acid residues and the positions of the 8 cysteines are identical with those of wheat purothionins. There is a high degree of homology in the primary structures of these proteins.

Amino acid sequences of two ferredoxins from Phytolacca esculenta. Gene duplication and speciation

The amino acid sequences of two ferredoxins from Phytolacca esculenta were determined by a combination of solid-phase sequencing and the conventional methods. Ferredoxins I and II were composed of 96 and 98 amino acid residues, respectively, and ferredoxin I showed sequence heterogeneity at two positions. The amino acid sequences of ferredoxins I and II from Phytolacca esculenta were very similar to those of corresponding ferredoxins I and II from Phytolacca americana. Amino acid differences among Phytolacca ferredoxins and other higher plant ferredoxins suggest that duplication of the ferredoxin gene occurred after the divergence of Phytolacca from other higher plants and preceded the separation of two species of Phytolacca.

Structural and evolution of chloroplast- and bacterial-type ferredoxins

Comparisons have been made between amino acid sequences of 26 chloroplast-type ferredoxins and 16 bacterial-type ferredoxins. Their structural characteristics are described and related to a three-dimensional structure of a chloroplast-type ferredoxin. Aspects of molecular evolution of these ferredoxins are presented together with a phylogenetic tree including both chloroplast- and bacterial-type ferredoxins.

The effects of Na+ and Mg2+ on the thermal denaturation of native and acetylated spinach ferredoxins

The effects of metal ions on the thermal denaturation and Mg2+ binding of native spinach ferredoxin and its acetylated derivative were investigated. The denaturation of ferredoxin in a metal-free solution at 40 degrees C was quickly prevented by the addition of Mg2+ or Na+ at appropriate concentrations. The metal concentrations required for 50% protection from thermal denaturation were 1.54 x 10(-4) M Mg2+ or 8.0 x 10(-3) M Na+ for native ferredoxin and 1.05 x 10(-3) M Mg2+ or 6.0 x 10(-2) M Na+ for acetylated ferredoxin. It was also found that native ferredoxin in the presence of over 20 mM Mg2+ was almost completely protected from thermal denaturation at 40 degrees C. The D-form which has been observed in acetylated ferredoxin by Masaki et al. (1977) (J. Biochem. 81, 1-9) was confirmed to be present in native ferredoxin at high temperature (49 degrees C) and is suggested to be an important form in the denaturation processes of the ferredoxin molecule.

Isolation and characterization of two ferredoxin-NADP+ reductases from Spirulina platensis

Two ferredoxin-NADP+ reductases (FNRs I and II) [EC 1.6.7.1] were purified from a blue-green alga, Spirulina platensis, by (NH4)2SO4 fractionation, gel filtration on Sephadex G-100 and DEAE-Sephadex A-50 chromatography. FNRs I and II were both FAD-containing enzymes with molecular weights of 33,000, and could photochemically reduce NADP+ to the same extent in the presence of S. platensis ferredoxin, using FNR-depleted membrane fragments of S. platensis. They had similar physical and enzymatic properties, except for chemical properties such as the amino (N)-terminal sequences and the patterns of their peptide maps. The significance of the presence of two FNRs in S. platensis as as of the multiple forms found in other organisms is discussed.

X-ray analysis of ferredoxin from Spirulina platensis. II. Chelate structure of active center

A chloroplast-type ferredoxin from Spirulina platenis crystallized in an orthorhombic system, space group C2221, with cell dimensions a=62.32, b=28.51, and c=108.08 A. The electron density map at 2.8 A resolution was prepared by using the best phase angles determined by the single isomorphous replacement method coupled with the anomalous dispersion method. The chelating structure of the acitve center was revealed as follows. Of the six cysteinyl residues in the molecule, Cys 41, Cys 4k, Cys 49, and Cys 79 are involved in the active center. Cys 41 and Cys 46 are coordinated to one iron atom, and Cys 49 and Cys 79 to the other iron atom. Only one of these cysteinyl residues, Cys 79, is comparatively apart from the other three in the amino acids sequence of the molecule, as found in the case of bacterial ferredoxin. It appears that the NH....S hydrogen bonds are around the active center, as in other non-heme iron sulfur proteins.

Purification of four pyruvate kinase isozymes of rats by affinity elution chromatography

1. Purification of four isozymes of pyruvate kinase (ATP:pyruvate 2-O-phosphotransferase, EC 2.7.1.40) L, M1, M2 and R was much improved to give good yields by affinity elution chromatography. The enzyme was eluted from a phosphocellulose column with 0.5 mM phosphoenolpyruvate. Types L, M2 and R were stabilized with fructose 1,6-diphosphate throughout the purification procedures. 2. The isozymes were crystallized under various conditions: types L and R were readily crystallized from medium of low ionic strength, types L, M1, and M2 were crystallized from ammonium sulfate solution in different forms in the presence and absence of phosphoenolpyruvate. Type M1 was also crystallized in different forms in the presence and absence of fructose 1,6-diphosphate. 3. Amino acid analyses showed that the compositions of types L and R, and of types M1 and M2, respectively, were very similar.

Amino acid sequences of two ferredoxins from pokeweed, Phytolacca americana

The amino acid sequences of two ferredoxins isolated from pokeweed, Phytolacca americana, were determined. Tryptic peptides of maleyl-carboxymethyl-ferredoxin I and carboxymethyl-ferredoxin II were prepared and analyzed. The large peptides were further digested with staphylococcal protease and chymotrypsin. Ferredoxins I and II were composed of 96 and 98 amino acid residues, respectively. Though ferredoxin I lacks tryptophan and methionine, ferredoxin II contains both of them. In a comparison of the amino acid sequences with those of other higher plant ferredoxins, ferredoxin I is one residue shorter than others at the carboxyl-terminus and ferredoxin II one longer than others at the amino-terminus. Ferredoxins I and II differ in 23 sites from each other and in 27 to 37 sites from other higher plant ferredoxins. This suggests that duplication of the ferredoxin gene occurred after the divergence of pokeweed from other higher plants. A phylogenetic tree including all other ferredoxins was constructed.

Horsetail (Equisetum telmateia) ferredoxins I and II. Amino acid sequences

Two ferredoxins were isolated from horsetail (Equisetum telmateia) and their amino acid sequences were determined by use of a sequence analyzer in combination with carboxypeptidase digestion and manual Edman degradation of tryptic peptides of carboxymethyl-ferredoxins. Ferredoxins I and II each had only four cysteine residues in a total of 95 and 93 residues, respectively. The amino-terminal residues of both ferredoxins were heterogeneous, but alanine was concluded to be their genuine terminal residue. The comparison of these isozymelike molecules showed 29 differences in amino acid residues with three inverted replacements. One gap was inserted in ferredoxin II at position 32 to align the ferredoxins with greatest homology. Despite the many differences in amino acid residues there was no difference in net charges of the two ferredoxins.

Horsetail (Equisetum arvense) ferredoxins I and II Amino acid sequences and gene duplication

Amino acid sequences of two ferredoxins isolated from Equisetum arvense were determined by conventional procedures. Ferredoxins I and II of E. arvense had 95 and 93 residues, respectively, and nearly identical sequences each with only one amino acid difference from ferredoxins. I and II of E. telmateia (1). The overall structural characteristics of these two ferredoxins were therefore very similar to those of E. telmateia ferredoxins. Ferredoxins I and II from E. arvense differ in 31 sites and those from E. telmateia in 29 sites from each other. These facts suggested that duplication of the ferredoxin gene in one organism occurred at an early evolutionary stage long before the divergence of the two horsetail species. The number of differences in amino acids between horsetail ferredoxins and other chloroplast-type ferredoxins indicated that the duplication occurred after divergence of horsetails from other plants. Comparing green plant ferredoxins, it was estimated that this gene duplication occurred about 250 million years ago. Some comments on the unique amino acid substitutions in horsetail ferredoxins are also presented.