Amino acid sequence similarity between spinach chloroplast and mammalian gluconeogenic fructose-1,6-bisphosphatase

High-level expression of recombinant pea chloroplast fructose-1,6-bisphosphatase and mutagenesis of its regulatory site

The cDNA fragment coding for mature chloroplast pea fructose-1,6-bisphosphatase [Fru(1,6)P2ase] was introduced by PCR into the expression vector pET-3d resulting in the construction pET-FBP. After transformation of BL21 (DE3) Escherichia coli cells by the pET-FBP plasmid and induction with isopropyl thio-beta-D-galactoside, high-level expression of the recombinant enzyme was achieved. The protein could be purified in three days by a simple procedure which includes heat treatment, ammonium sulfate fractionation, DEAE Sephacel and ACA 44 chromatographies with a yield of 20 mg/l culture. In every respect, the recombinant enzyme was similar to plant chloroplast Fru(1,6)P2ase and, in particular, its reactivity with Mg2+ and redox regulatory properties were conserved. In a second series of experiments based on three-dimensional modeling of the chloroplast protein and sequence alignments, two cysteine residues of the recombinant enzyme (Cys173 and Cys178) were mutated into serine residues. An active enzyme, which did not respond to thiol reagents and to light activation, was obtained, confirming the putative regulatory role of the insertional sequence characteristic of the chloroplast enzyme.

Plant fructose-1,6-bisphosphatases: characteristics and properties

In this minireview the properties and characteristics of plant fructose-1,6-bisphosphatases (D-fructose-1,6-bisphosphatase 1-phosphohydrolase, EC 3.1.3.11) are discussed. The properties and characteristics of the chloroplastic and cytoplasmic forms of the enzyme are reviewed. For purposes of comparison some reference is made to fructose-1,6-bisphosphatases from other species.

Isolation and sequence analysis of the cDNA for pig kidney fructose 1,6-bisphosphatase

A full-length clone of pig kidney fructose 1,6-bisphosphatase (D-fructose-1,6-bisphosphate 1-phosphohydrolase, EC 3.1.3.11) was isolated by screening a cDNA library for complementation of an Escherichia coli fbp deletion mutation. The open reading frame of 1011 bases corresponds to 337 amino acids, two more than have been previously reported [Marcus, F., Edelstein, I., Reardon, I. & Heinrikson, R. L. (1982) Proc. Natl. Acad. Sci. USA 79, 7161-7165]. The extra two amino acids (Ala-Lys) are located at the C-terminal end of the protein as an extension. Comparison of the deduced amino acid sequence with the reported (see above) and revised amino acid sequence [Harrsch, P. B., Kim, Y., Fox, J. L. & Marcus, F. (1985) Biochem. Biophys. Res. Commun. 133, 520-526] indicates three differences in addition to the C-terminal extension. Gln-20, Thr-96, and Asn-199 in the amino acid sequence are found to be Glu, Ser, and Asp, respectively. Since the x-ray structure of the pig kidney enzyme has been reported, the cDNA clone will allow the construction of site-specific mutants to help test possible structure-function relationships in this important metabolic enzyme.

Amino acid sequence of spinach chloroplast fructose-1,6-bisphosphatase

The amino acid sequence of the spinach chloroplast fructose-1,6-bisphosphatase (FBPase) subunit has been determined. Placement of the 358 residues in the polypeptide chain was based on automated Edman degradation of the intact protein and of peptides obtained by enzymatic or chemical cleavage. The sequence of spinach chloroplast FBPase shows clear homology (ca. 40%) to gluconeogenic (mammalian, yeast, and Escherichia coli) fructose-1,6-bisphosphatases and 80% homology with the wheat chloroplast enzyme. The two chloroplast enzymes show near the middle of the structure a unique sequence insert probably involved in light-dependent regulation of the chloroplast FBPase enzyme activity. This sequence insert contains two cysteines separated by only 4 amino acid residues, a characteristic feature of some enzymes containing redox-active cysteines. The recent X-ray crystallographic resolution of pig kidney FBPase (H. Ke, C. M. Thorpe, B. A. Seaton, F. Marcus, and W. N. Lipscomb, 1989, Proc. Natl. Acad. Sci. USA 86, 1475-1479) has allowed the discussion of the amino acid sequence of spinach chloroplast FBPase in structural terms. It is to be noted that most of pig kidney FBPase residues shown to be either at (or close to) the sugar bisphosphate binding site or located at the negatively charged metal binding pocket are conserved in the chloroplast enzyme. The unique chloroplast FBPase insert presumably involved in light-dependent activation of the enzyme via a thioredoxin-linked mechanism can be accommodated in the surface of the FBPase molecule.

Structure refinement of fructose-1,6-bisphosphatase and its fructose 2,6-bisphosphate complex at 2.8 A resolution

The structures of the native fructose-1,6-bisphosphatase (Fru-1,6-Pase), from pig kidney cortex, and its fructose 2,6-bisphosphate (Fru-2,6-P2) complexes have been refined to 2.8 A resolution to R-factors of 0.194 and 0.188, respectively. The root-mean-square deviations from the standard geometry are 0.021 A and 0.016 A for the bond length, and 4.4 degrees and 3.8 degrees for the bond angle. Four sites for Fru-2,6-P2 binding per tetramer have been identified by difference Fourier techniques. The Fru-2,6-P2 site has the shape of an oval cave about 10 A deep, and with other dimensions about 18 A by 12 A. The two Fru-2,6-P2 binding caves of the dimer in the crystallographically asymmetric unit sit next to one another and open in opposite directions. These two binding sites mutually exchange their Arg243 side-chains, indicating the potential for communication between the two sites. The beta, D-fructose 2,6-bisphosphate has been built into the density and refined well. The oxygen atoms of the 6-phosphate group of Fru-2,6-P2 interact with Arg243 from the adjacent monomer and the residues of Lys274, Asn212, Tyr264, Tyr215 and Tyr244 in the same monomer. The sugar ring primarily contacts with the backbone atoms from Gly246 to Met248, as well as the side-chain atoms, Asp121, Glu280 and Lys274. The 2-phosphate group interacts with the side-chain atoms of Ser124 and Lys274. A negatively charged pocket near the 2-phosphate group includes Asp118, Asp121 and Glu280, as well as Glu97 and Glu98. The 2-phosphate group showed a disordered binding perhaps because of the disturbance from the negatively charged pocket. In addition, Asn125 and Lys269 are located within a 5 A radius of Fru-2,6-P2. We argue that Fru-2,6-P2 binds to the active site of the enzyme on the basis of the following observations: (1) the structure similarity between Fru-2,6-P2 and the substrate; (2) sequence conservation of the residues directly interacting with Fru-2,6-P2 or located at the negatively charged pocket; (3) a divalent metal site next to the 2-phosphate group of Fru-2,6-P2; and (4) identification of some active site residues in our structure, e.g. tyrosine and Lys274, consistent with the results of the ultraviolet spectra and the chemical modification. The structures are described in detail including interactions of interchain surfaces, and the chemically modifiable residues are discussed on the basis of the refined structures.(ABSTRACT TRUNCATED AT 400 WORDS)

Chloroplast fructose-1,6-bisphosphatase: the product of a mosaic gene

We show here that light stimulates the expression of nuclear genes in wheat leaves for chloroplast fructose-1,6-bisphosphatase (FBPase) and describe a sequence of amino acids in this enzyme which may be responsible, via thioredoxin, for the light regulation of its activity. This data results from (a) our isolation and characterization of a cDNA of this enzyme which contains its entire coding sequence, and (b) our use of this cDNA as a probe to detect mRNA levels in wheat plants subjected to different light regimes. The similarity in amino acid sequence of the encoded enzyme from diverse sources suggests that the FBPase genes all had a common origin. However, their control sequences have been adjusted so that they are appropriately expressed and their coding sequences modified so that the enzymic activity of their products are suitably regulated in the particular cellular environment in which they must function. The light-activated regulatory sequences in the gene for the chloroplast protein have probably come together by a shuffling of DNA segments.

Comparative amino acid sequence of fructose-1,6-bisphosphatases: identification of a region unique to the light-regulated chloroplast enzyme

Chloroplast fructose-1,6-bisphosphatase (Fru-P2-ase) is an essential enzyme in the photosynthetic pathway of carbon dioxide fixation into sugars. The properties of the chloroplast enzyme are clearly distinct from cytosolic gluconeogenic Fru-P2-ases. Light-dependent activation by way of a ferredoxin/thioredoxin system and insensitivity to AMP inhibition are distinctive characteristics of the chloroplast enzyme. However, the chloroplast enzyme shows a high degree of amino acid sequence similarity to gluconeogenic Fru-P2-ases. Sequence data reported for a total of 285 residues (approximately 75% of the structure) of the spinach chloroplast enzyme reveals a 46% amino acid sequence identity with pig kidney Fru-P2-ase. We now report the amino acid sequence of a region consisting of 46 additional residues. This region is located near the middle of the primary structure of the enzyme and it includes a 16-residue insert not present in other Fru-P2-ases. This sequence insert has two cysteines separated by only 4 amino acid residues (Cys-Val-Val-Asn-Val-Cys), a characteristic feature of at least three other enzymes containing redox-active cysteines. It appears likely that this region of chloroplast Fru-P2-ase is involved in light-dependent activation.

In vitro phosphorylation of fructose-1,6-bisphosphatase from rabbit and pig liver with cyclic AMP-dependent protein kinase

Homogeneous preparations of fructose-1,6-bisphosphatase from mouse, man, rabbit, pig, and rat were tested as substrates for cyclic AMP-dependent protein kinase. Up to 1 mol of [32P]phosphate per mole enzyme subunit was incorporated into fructose-1,6-bisphosphatase from pig and rabbit liver, which should be compared with 2.6 mol of phosphate per mole enzyme subunit in the case of the rat liver enzyme. The phosphorylation of fructose-1,6-bisphosphatase from the livers of man and mouse was negligible. Phosphorylation of pig and rabbit fructose-1,6-bisphosphatase decreased the apparent Km for fructose-1,6-bisphosphate, but in contrast to the case of the rat liver enzyme it did not change the inhibition constants for AMP and fructose-2,6-bisphosphate. The phosphorylation sites in rabbit and pig liver fructose-1,6-bisphosphatase were located close to the carboxyterminal of the polypeptide chains, since trypsin treatment of the phosphorylated enzyme quantitatively removed all of the protein-bound radioactivity without significantly altering the subunit molecular weight and with a maintained neutral pH optimum.

Amino acid sequence similarity between malate dehydrogenases (NAD) and pea chloroplast malate dehydrogenase (NADP)

Purified pea chloroplast malate dehydrogenase (NADP) was reduced, S-pyridylethylated with 4-vinyl-pyridine and cleaved with trypsin. The resulting peptides were separated by reversed-phase high-performance liquid chromatography. Several of these peptides were subjected to automated Edman degradation. The sequences obtained were compared to the published primary structures of malate dehydrogenase from the thermophilic bacterium Thermus flavus and with the sequence of heart mitochondrial and cytoplasmic malate dehydrogenase (NAD). Most peptides from choroplast malate dehydrogenase (NADP) showed high homology with sequences of the other malate dehydrogenases, especially with those of the bacterial enzyme. One of the sequenced peptides contains the active-site histidine residue which is conserved in all malate dehydrogenases. Our results suggest a common evolutionary origin for all malate dehydrogenases despite their different coenzyme specificities and regulatory properties. The sequenced peptides which revealed no homology were either located at the amino-terminal or at the carboxy-terminal region of chloroplast malate dehydrogenase (NADP). These novel sequences are most likely plant-specific extensions of an ancestral malate dehydrogenase and may be responsible for the unique light-dependent activation of the chloroplast enzyme.

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.

Amino acid sequence homology among fructose-1,6-bisphosphatases

The hydrolysis of fructose 1,6-bisphosphate to fructose 6-phosphate is a key reaction of carbohydrate metabolism. The enzyme that catalyzes this reaction, fructose-1,6-bisphosphatase, appears to be present in all forms of living organisms. Regulation of the enzyme activity, however, occurs by a variety of distinct mechanisms. These include AMP inhibition (most sources), cyclic AMP-dependent phosphorylation (yeast), and light-dependent activation (chloroplast). In the present studies, we have made a comparison of the primary structure of mammalian fructose-1,6-bisphosphatase with the sequence of peptides isolated from the yeast Saccharomyces cerevisiae, Escherichia coli, and spinach chloroplast enzymes. Our results demonstrate a high degree of sequence homology, suggesting a common evolutionary origin for all fructose-1,6-bisphosphatases.