Purification of a Complex of Alkaline Fructose 1, 6-Bisphosphatase and Phosphoribulokinase from Rhodospirillum rubrum

Application of short column gel permeation in the study of protein-protein interactions

A simple and rapid procedure based on the gel filtration principle is described together with its applicability to the study of protein-protein interactions including subunit-subunit and enzyme-enzyme interactions. Using this procedure, it is shown that phosphoglycerate kinase (PGK) and glyceraldehyde-3-phosphate dehydrogenase (GPDH) interact with a stoichiometry of one PGK molecule combining with one monomeric subunit of GPDH. This interaction has been observed with both enzymes being from the same, as well as from different, species. The Kd values for rabbit muscle PGK and porcine muscle GPDH complex and that for the rabbit muscle PGK and yeast GPDH complex are found to be (4.5 +/- 2.0) x 10(-7) M and (6.5 +/- 1.7) x 10(-7) M, respectively. The specificity of bienzyme association is stronger when enzymes are from the same species than when they are from different species.

Coordination of catalytic activities within enzyme complexes

If two enzymes are physically and permanently associated as a bi-enzyme complex and if these enzymes catalyze non-consecutive chemical reactions, either of these reactions may inhibit or activate the other. If these reactions belong to two different metabolic cycles, the functioning of one of these cycles will control the fine tuning of the other. Thus simple kinetic considerations lead to the conclusion that, owing to the spatial organization of enzymes as multimolecular complexes, a fine tuning and a coordination of different metabolic networks, or cycles, may be exerted. It thus appears that channelling of reaction intermediates within a multienzyme complex does not represent the only functional advantage brought about by this type of spatial molecular organization.

Complementation analysis and regulation of CO2 fixation gene expression in a ribulose 1,5-bisphosphate carboxylase-oxygenase deletion strain of Rhodospirillum rubrum

A ribulose 1,5-bisphosphate carboxylase-oxygenase (RubisCO) deletion strain of Rhodospirillum rubrum that was incapable of photolithoautotrophic growth was constructed. Photoheterotrophic growth, however, was possible for the R. rubrum RubisCO deletion strain when oxidized carbon compounds such as malate were supplied. The R. rubrum RubisCO-deficient strain was not complemented to photolithoautotrophic growth by various R. rubrum DNA fragments that contain the gene encoding RubisCO, cbbM. When the R. rubrum cbbM deletion strain harbored plasmids containing R. rubrum DNA inserts with at least 2.0 kb preceding the translational start site of the cbbM gene, RubisCO activity and RubisCO antigen were detected. Lack of RubisCO expression was therefore not the cause for the failure to complement the cbbM mutant strain. Interestingly, DNA fragments encoding either of two complete Calvin-Benson-Bassham CO2- fixation (cbb) gene operons from Rhodobacter sphaeroides were able to complement the R. rubrum RubisCO deletion strain to photolithoautotrophic growth. The same R. rubrum DNA fragments that failed to complement the R. rubrum cbbM deletion strain successfully complemented the RubisCO deletion strain of R. sphaeroides, pointing to distinct differences in the regulation of metabolism and the genetics of photolithoautotrophic growth in these two organisms. A number of cbb genes were identified by nucleotide sequence analysis of the region upstream of cbbM. Included among these was an open reading frame encoding a cbbR gene showing a high degree of sequence similarity to known lysR-type CO2 fixation transcriptional activator genes. The placement and orientation of the cbbR transcriptional regulator gene in R. rubrum are unique.

Chloroplast phosphoribulokinase associates with yeast phosphoriboisomerase in the presence of substrate

Pea chloroplastic phosphoribulokinase and yeast phosphoriboisomerase partition independently of one another in a two-phase polyethyleneglycol, dextran system, but apparent interaction is seen when ribose-5-phosphate is added to the two-phase system. It appears that the pea leaf kinase recognizes yeast isomerase when it is carrying metabolite.

The form II fructose 1,6-bisphosphatase and phosphoribulokinase genes form part of a large operon in Rhodobacter sphaeroides: primary structure and insertional mutagenesis analysis

Fructose 1,6-bisphosphatase (FBPase) and phosphoribulokinase (PRK) are two key enzymes of the reductive pentose phosphate pathway or Calvin cycle of photosynthetic carbon dioxide assimilation. Early studies had indicated that the properties of enzymes isolated from photosynthetic bacteria were clearly distinct from those of enzymes obtained from the chloroplasts of higher plants [for a review, see Tabita (1988)]. The eucaryotic enzymes, which are light activated by the thioredoxin/ferredoxin system (Buchanan, 1980), were each shown to contain a putative regulatory amino acid sequence (Marcus et al., 1988; Porter et al., 1988). The enzymes from photosynthetic bacteria are not controlled by the thioredoxin/ferredoxin system but exhibit complex kinetic properties and, in the case of PRK, there is an absolute requirement of NADH for activity. In the photosynthetic bacterium Rhodobacter sphaeroides, the structural genes of the Calvin cycle, including the genes that encode FBPase (fbp) and PRK (prk), are found in two distinct clusters, and the fbp and prk genes are closely associated in each cluster. In the present investigation, we have determined the nucleotide sequence of the fbpB and prkB genes of the form II cluster and have compared the deduced amino acid sequences to previously determined sequences of light-activated enzymes from higher plants and from other eucaryotic and procaryotic sources. In the case of FBPase, there are several regions that are conserved in the R. sphaeroides enzymes, including a protease-sensitive area located in a region equivalent to residues 51-71 of mammalian FBPase.(ABSTRACT TRUNCATED AT 250 WORDS)

Localization and mapping of CO2 fixation genes within two gene clusters in Rhodobacter sphaeroides

Two fructose 1,6-bisphosphatase structural genes (fbpA and fbpB) have been identified within two unlinked gene clusters that were previously shown to contain the Rhodobacter sphaeroides sequences that code for form I and form II ribulose 1,5-bisphosphate carboxylase-oxygenase and phosphoribulokinase. The fbpA and fbpB genes were localized to a region immediately upstream from the corresponding prkA and prkB sequences and were found to be transcribed in the same direction as the phosphoribulokinase and ribulose 1,5-bisphosphate carboxylase-oxygenase genes based on inducible expression of fructose 1,6-bisphosphatase activity directed by the lac promoter. A recombinant plasmid was constructed that contained the tandem fbpA and prkA genes inserted downstream from the lac promoter in plasmid pUC18. Both gene products were expressed in Escherichia coli upon induction of transcription with isopropyl beta-D-thiogalactoside, demonstrating that the two genes can be cotranscribed. A Zymomonas mobilis glyceraldehyde 3-phosphate-dehydrogenase gene (gap) hybridized to a DNA sequence located approximately 1 kilobase upstream from the form II ribulose 1,5-bisphosphate carboxylase-oxygenase gene. Although no corresponding gap sequence was found within the form I gene cluster, an additional region of homology was detected immediately upstream from the sequences that encode the form I and form II ribulose 1,5-bisphosphate carboxylase-oxygenases.

An immunological method for quantitative determination of photosynthetic fructose-1,6-bisphosphatase in leaf crude extracts

An immunological method for quantitative determination of photosynthetic fructose-1,6-bisphosphatase in crude extracts of leaves is proposed. It is based on the ELISA technique, and offers two modifications. A non-competitive technique has a higher sensitivity and is the right option for samples of low fructose-1,6-bisphosphatase content. However, this method is not sufficiently specific when the total protein is higher than 5 μg/cm(3); so, despite its lower sensitivity, in these circumstances a competitive technique is more suitable. Thus photosynthetic fructose-1,6-bisphosphatase can be measured without interferences from the gluconeogenic cytosolic enzyme of the photosynthetic cell or from a non-specific phosphatase present in the chloroplast.

Pyridine nucleotide control and subunit structure of phosphoribulokinase from photosynthetic bacteria

With one exception, phosphoribulokinase from the Rhodospirillaceae requires reduced nicotinamide adenine dinucleotide for maximum activity. This mode of regulation is unique to the facultatively anaerobic photoorganotrophic photosynthetic bacteria, since the phosphoribulokinase from oxygen-evolving photosynthetic species is not subject to activation by reduced nicotinamide adenine dinucleotide. The enzyme was purified of fructose bisphosphatase activity from Rhodopseudomonas capsulata by means of affinity chromatography and was shown to have a native molecular weight of about 220,000. The homogeneous enzyme is composed of a single size polypeptide of 36,000 molecular weight. This study represents the first time the subunit structure of phosphoribulokinase has been determined from any source.

Metabolic regulation in Pseudomonas oxalaticus OX1. Enzyme and coenzyme concentration changes during substrate transition experiments

Metabolic control associated with diauxic growth of Pseudomonas oxalaticus in batch cultures on mixtures of formate and oxalate was investigated by measuring intracellular enzyme and coenzyme concentrations and QO2 values during transition experiments from oxalate to formate and vice versa. In transition from oxalate to formate oxalyl-CoA reductase concentration declined after the exhaustion of oxalate and ribulose-1,5-diphosphate carboxylase and 14CO2 fixation appeared upon addition of formate. In the reciprocal transition, ribulose-1,5-diphosphate carboxylase and 14CO2 fixation rate declined sharply after formate exhaustion, and oxalyl-CoA reductase appeared only after addition of oxalate. The intracellular NAD and NADP concentrations measured in the same experiments are reported. At substrate exhaustion the proportion of NAD in the reduced form fell from 15-20% to 2%. On addition of formate to an oxalate-starved culture there was an immediate increase in the proportion of NADH to 50%; such an increase was not observed in the reverse experiment.

Simultaneous operation of three catabolic pathways in the metabolism of glucose by Thiobacillus A2

Enzymes essential to the operation of the Embden-Meyerhof glycolytic pathway, the Entner-Duodoroff pathway and oxidative pentose phosphate pathway were present in Thiobacillus A2 grown on glucose and other sugars. Radiorespirometry under various conditions with Thiobacillus A2 oxidising glucose specifically labelled with 14C in carbon atoms 1, 2, 3, 3 + 4, 6 or universally labelled demonstrated the simultaneous operation of the Embden-Meyerhof (48%), Entner-Doudoroff (28%), and pentose phosphate (24%) pathways in release of carbon dioxide from glucose. Growth on succinate, or autotrophically on formate or thiosulphate resulted in repression of most enzymes of the pathways, but high aldolase levels were retained indicating its role in gluconeogenesis and the Calvin cycle. Different fructose diphosphatase activities were found in succinate- and thiosulphate-grown organisms. The results indicate that all three major catabolic pathways for glucose function in Thiobacillus A2 grown on sugars. Thiobacillus acidophilus showed a different radiorespirometric pattern and apparently used the Entner-Duodoroff (64.5%) and pentose phosphate (35.5%) pathways, but showed unusually high release of carbon atom 6, as was also found for T. ferrooxidans.

Purification and regulatory properties of fructose 1,6-diphosphatase from Hydrogenomonas eutropha

Fructose diphosphatase of Hydrogenomonas eutropha H 16, produced during autotrophic growth, was purified 247-fold from extracts of cells. The molecular weight of the enzyme was estimated to be 170,000. The enzyme showed a pH optimum of 8.5 in both crude extracts and purified preparation. The shape of the pH curve was not changed in the presence of ethylenediaminetetraacetic acid. The enzyme required Mg(2+) for activity. The MgCl(2) saturation curve was sigmoidal and the degree of positive cooperativity increased at lower fructose diphosphate concentrations. Mn(2+) can replace Mg(2+), but maximal activity was lower than that observed with Mg(2+) and the optimal concentration range was narrow. The fructose diphosphate curve was also sigmoidal. The purified enzyme also hydrolyzed sedoheptulose diphosphate but at a much lower rate than fructose diphosphate. The enzyme was not inhibited by adenosine 5'-monophosphate but was inhibited by ribulose 5-phosphate and adenosine 5'-triphosphate. Adenosine 5'-triphosphate did not affect the degree of cooperativity among the sites for fructose diphosphate. The inhibition by adenosine 5'-triphosphate was mixed and by ribulose 5-phosphate was noncompetitive. An attempt was made to correlate the properties of fructose diphosphatase from H. eutropha with its physiological role during autotrophic growth.