Purification procedure and N-terminal amino acid sequence of yeast malate dehydrogenase isoenzymes

Cat8 and Sip4 mediate regulated transcriptional activation of the yeast malate dehydrogenase gene MDH2 by three carbon source-responsive promoter elements

Malate dehydrogenase isoenzymes are localized in different cellular compartments and fulfil important functions in intermediary metabolism. In the yeast Saccharomyces cerevisiae, three malate dehydrogenase genes, MDH1, MDH2 and MDH3, encoding mitochondrial, cytosolic and peroxisomal variants, have been identified. We demonstrate the importance of transcriptional activators Hap4, Cat8 and Pip2 for the carbon source-dependent regulation of MDH1, MDH2 and MDH3, respectively. The control region of the MDH2 gene required for gluconeogenic growth with C(2) substrates contains three sequence elements similar to the previously identified carbon source-responsive element (CSRE). In a synthetic test system, each of these sequences turned out to be a weak UAS element showing a strong synergism when present in multiple copies. Cumulative mutagenesis of the natural MDH2 promoter confirmed the contribution of all three elements to transcriptional derepression under non-fermentative growth conditions. The DNA-binding domains of zinc cluster proteins Cat8 and Sip4 synthesized in Escherichia coli could interact in vitro with CSRE motifs of MDH2. This result was confirmed by binding assays using protein extracts from yeast. Deregulated variants of Cat8 and Sip4 modified by heterologous transcriptional activation domains were able to alleviate glucose repression of MDH2 substantially. Although Sip4 turned out as the less effective activator, our findings demonstrate the general significance of both proteins for expression of gluconeogenic structural genes.

Molecular biology of trehalose and the trehalases in the yeast Saccharomyces cerevisiae

The present state of knowledge of the role of trehalose and trehalose hydrolysis catalyzed by trehalase (EC 3.2.1.28) in the yeast Saccharomyces cerevisiae is reviewed. Trehalose is believed to function as a storage carbohydrate because its concentration is high during nutrient limitations and in resting cells. It is also believed to function as a stress metabolite because its concentration increases during certain adverse environmental conditions, such as heat and toxic chemicals. The exact way trehalose may perform the stress function is not understood, and conditions exist under which trehalose accumulation and tolerance to certain stress situations cannot be correlated. Three trehalases have been described in S. cerevisiae: 1) the cytosolic neutral trehalase encoded by the NTH1 gene, and regulated by cAMP-dependent phosphorylation process, nutrients, and temperature; 2) the vacuolar acid trehalase encoded by the ATH1 gene, and regulated by nutrients; and 3) a putative trehalase Nth1p encoded by the NTH2 gene (homolog of the NTH1 gene) and regulated by nutrients and temperature. The neutral trehalase is responsible for intracellular hydrolysis of trehalose, in contrast to the acid trehalase, which is responsible for utilization of extracellular trehalose. The role of the putative trehalase Nth2p in trehalose metabolism is not known. The NTH1 and NTH2 genes are required for recovery of cells after heat shock at 50 degrees C, consistent with their heat inducibility and sequence similarity. Other stressors, such as toxic chemicals, also induce the expression of these genes. We therefore propose that the NTH1 and NTH2 genes have stress-related function and the gene products may be called stress proteins. Whether the stress function of the trehalase genes is linked to trehalose is not clear, and possible mechanisms of stress protective function of the trehalases are discussed.

Sequence analysis of a 13.4 kbp fragment from the left arm of chromosome XV reveals a malate dehydrogenase gene, a putative Ser/Thr protein kinase, the ribosomal L25 gene and four new open reading frames

A 13421 bp fragment located near the left telomere of chromosome XV (cosmid pEOA461) has been sequenced. Seven non-overlapping open reading frames (ORFs) encoding polypeptides longer than 100 residues have been found (AOB859, AOC184, AOE375, AOX142i, AOE423, AOA476 and AOE433). An additional ORF (AOE131) is found within AOA476. Three of them (AOC184, AOA476 and AOE433) show no remarkable identity with proteins deposited in the data banks. ORF AOB859 is quite similar to a hypothetical yeast protein of similar size located in chromosome VI, particularly within the C-terminal half. AOE375 encodes a new member of the glycogen synthase kinase-3 subfamily of Ser/Thr protein kinases. AOX142i is the gene encoding the previously described ribosomal protein L25. AOE423 codes for a protein virtually identical to the MDH2 malate dehydrogenase isozyme. However, our DNA sequence shows a single one-base insertion upstream of the reported initiating codon. This would produce a larger ORF by extending 46 residues the N-terminus of the protein. The existence of this insertion has been confirmed in three different yeast strains, including FY1679.

Resolution of Fusarium sporotrichioides Proteins by Two-Dimensional Polyacrylamide Gel Electrophoresis and Identification by Sequence Homology Comparison in Protein Data Base

Proteins from Fusarium sporotrichioides M-1-1, a T2-toxin-producing strain, were separated by two-dimensional polyacrylamide gel electrophoresis. One thousand two hundred and forty-four protein spots were resolved and 103 protein spots were subjected to N-terminal sequencing. Fifty-eight protein spots were sequenced and 48 proteins were observed to have blocked N termini. Forty out of 58 sequenced proteins were identified by homology search against the PIR protein sequence data base and protein superfamily data base, while the residual 18 sequences were not identified. Twenty-seven of the N-terminal-blocked proteins were subjected to mild anhydrous hydrazine vapor deblocking. Twenty-four spots were not deblocked indicating the presence of acyl groups at the N termini, while 3 proteins were deblocked showing the blocked group to be pyrroglutamyl carboxylic acid residues. The results can provide a more global view of cellular genetic expression than any other technique. The created data may offer a unique opportunity to link information with DNA sequence data. Copyright 1995 S. Karger AG, Basel

Malate dehydrogenase from Chlorobium vibrioforme, Chlorobium tepidum, and Heliobacterium gestii: purification, characterization, and investigation of dinucleotide binding by dehydrogenases by use of empirical methods of protein sequence analysis

Malate dehydrogenase (MDH; EC 1.1.1.37) from strain NCIB 8327 of the green sulfur bacterium Chlorobium vibrioforme was purified to homogeneity by triazine dye affinity chromatography followed by gel filtration. Purification of MDH gave an approximately 1,000-fold increase in specific activity and recoveries of typically 15 to 20%. The criteria of purity were single bands on sodium dodecyl sulfate (SDS) and nondenaturing polyacrylamide electrophoresis (PAGE) and the detection of a single N terminus in an Edman degradation analysis. MDH activity was detected in purified preparations by activity staining of gels in the direction of malate oxidation. PAGE and gel filtration (Sephadex G-100) analyses showed the native enzyme to be a dimer composed of identical subunits both at room temperature and at 4 degrees C. The molecular weight of the native enzyme as estimated by gel filtration was 77,000 and by gradient PAGE was 74,000. The subunit molecular weight as estimated by SDS-gradient PAGE was 37,500. N-terminal sequences of MDHs from C. vibrioforme, Chlorobium tepidum, and Heliobacterium gestii are presented. There are obvious key sequence similarities in MDHs from the phototrophic green bacteria. The sequences presented probably possess a stretch of amino acids involved in dinucleotide binding which is similar to that of Chloroflexus aurantiacus MDH and other classes of dehydrogenase enzymes but unique among MDHs.

Isolation, nucleotide sequence analysis, and disruption of the MDH2 gene from Saccharomyces cerevisiae: evidence for three isozymes of yeast malate dehydrogenase

The major nonmitochondrial isozyme of malate dehydrogenase (MDH2) in Saccharomyces cerevisiae cells grown with acetate as a carbon source was purified and shown by sodium dodecyl sulfate-polyacrylamide gel electrophoresis to have a subunit molecular weight of approximately 42,000. Enzyme assays and an antiserum prepared against the purified protein were used to screen a collection of acetate-nonutilizing (acetate-) yeast mutants, resulting in identification of mutants in one complementation group that lack active or immunoreactive MDH2. Transformation and complementation of the acetate- growth phenotype was used to isolate a plasmid carrying the MDH2 gene from a yeast genomic DNA library. The amino acid sequence derived from complete nucleotide sequence analysis of the isolated gene was found to be extremely similar (49% residue identity) to that of yeast mitochondrial malate dehydrogenase (molecular weight, 33,500) despite the difference in sizes of the two proteins. Disruption of the MDH2 gene in a haploid yeast strain produced a mutant unable to grow on minimal medium with acetate or ethanol as a carbon source. Disruption of the MDH2 gene in a haploid strain also containing a disruption in the chromosomal MDH1 gene encoding the mitochondrial isozyme produced a strain unable to grow with acetate but capable of growth on rich medium with glycerol as a carbon source. The detection of residual malate dehydrogenase activity in the latter strain confirmed the existence of at least three isozymes in yeast cells.

Isolation, nucleotide sequence analysis, and disruption of the MDH2 gene from Saccharomyces cerevisiae: evidence for three isozymes of yeast malate dehydrogenase

The major nonmitochondrial isozyme of malate dehydrogenase (MDH2) in Saccharomyces cerevisiae cells grown with acetate as a carbon source was purified and shown by sodium dodecyl sulfate-polyacrylamide gel electrophoresis to have a subunit molecular weight of approximately 42,000. Enzyme assays and an antiserum prepared against the purified protein were used to screen a collection of acetate-nonutilizing (acetate-) yeast mutants, resulting in identification of mutants in one complementation group that lack active or immunoreactive MDH2. Transformation and complementation of the acetate- growth phenotype was used to isolate a plasmid carrying the MDH2 gene from a yeast genomic DNA library. The amino acid sequence derived from complete nucleotide sequence analysis of the isolated gene was found to be extremely similar (49% residue identity) to that of yeast mitochondrial malate dehydrogenase (molecular weight, 33,500) despite the difference in sizes of the two proteins. Disruption of the MDH2 gene in a haploid yeast strain produced a mutant unable to grow on minimal medium with acetate or ethanol as a carbon source. Disruption of the MDH2 gene in a haploid strain also containing a disruption in the chromosomal MDH1 gene encoding the mitochondrial isozyme produced a strain unable to grow with acetate but capable of growth on rich medium with glycerol as a carbon source. The detection of residual malate dehydrogenase activity in the latter strain confirmed the existence of at least three isozymes in yeast cells.

Isolation and primary structure of the gene encoding fructose-1,6-bisphosphatase from Saccharomyces cerevisiae

The gene encoding Saccharomyces cerevisiae fructose-1,6-bisphosphatase (FBP1) was isolated. Constructed fbp1::HIS3 null mutants were unable to grow with ethanol, and growth was restored after transformation with the cloned fbp gene. The gene codes for a protein of 347 amino acid residues with an Mr of 38131. Homology with the pig kidney cortex and the sheep liver enzyme is 47.7% and 46.6%, respectively, within a central core of 328 amino acid residues. The cloned promoter size was 318 bp and allowed only low level expression of the gene. This indicates a positive activation site (UAS) upstream of the cloned DNA fragment.

Cloning and sequence of the mdh structural gene of Escherichia coli coding for malate dehydrogenase

The malate dehydrogenase gene of Escherichia coli, which is susceptible to catabolite and anaerobic repression, has been cloned using plasmic pLC32-38 of Clarke and Carbon (1976). The nucleotide sequence was determined of a 2.47 kbp fragment, containing the mdh structural gene. All information necessary for expression of the mdh structural gene was mapped within a 1.3 kbp SphI-BstEII fragment. Compared with the untransformed wild type, transformations with pUC19 vector, containing this fragment, gave up to 40-fold more malate dehydrogenase activity in both E. coli wild type and mdh mutant recipients. Catabolite repression was not affected in the transformants. A possible CRP binding site in the promotor region of the mdh gene provides evidence for a co-regulation with fumA gene, the structural gene of fumarase, which is also subject to catabolite repression. The structures for transcription initiation and termination were similar to those previously described for E. coli. Amino acid sequence homologies between pro- and eucaryotic malate dehydrogenases are discussed.