Molecular analysis of the structural gene for yeast transaldolase

Abstract

We have cloned the structural gene for yeast transaldolase. Transformants carrying the TALl gene on a multicopy plasmid over-produced transaldolase. A deletion mutant which was constructed using the cloned gene did not show any detectable transaldolase activity in vitro. Furthermore, both transaldolase isoenzymes which were detected in wild-type crude extracts by immunoblotting were missing in the deletion mutants. Thus, TALl is the only transaldolase structural gene in yeast.TALI is not an essential gene. Deletion of the transaldolase gene did not affect growth on complete media with different carbon sources or on synthetic media. However, the transaldolase-deficient strains accumulated sedoheptulose 7-phosphate, an intermediate of the pentose-phosphate pathway. Mutants lacking both transaldolase and phosphoglucose isomerase grew more slowly than the single mutants. They accumulated more sedoheptulose 7-phosphate on medium containing fructose than on glucose medium. This shows that fructose 6-phosphate and glyceraldehyde 3-phosphate, metabolites of glycolysis, can enter the nonoxidative part of the pentose-phosphate pathway.

Transaldolase B of Escherichia coli K-12: cloning of its gene, talB, and characterization of the enzyme from recombinant strains

“…The sequence of TAL B (EcoB [35], DDBJ 10483 [this study]), partial sequences from TAL A (EcoA [29]), and C-terminal-derived sequence of E. coli (ORF1) preceding gene tktB [11] are shown. Sequences of TAL from S. cerevisiae (Sce [27]), K. lactis (Klac [12]), and humans (Hum [2]) and the sequence of an as yet unidentified cDNA clone from A. thaliana (Ath [22,23]) are given. For comparison with bacterial class I aldolases, the sequence of fructose-1,6-bisphosphate aldolase (ScFda of Staphylococcus carnosus [33]) is aligned but not included in the determination of conserved residues.…”

“…5. TAL B shows 53% identical amino acid residues to the S. cerevisiae sequence (27), 55% identical to Kluyveromyces lactis (12), and a remarkable 55% identical to a human cDNA clone (2). A database search (TBLASTN program of EMBL HUSAR, Heidelberg, Germany) gave significant scores with these three sequences and additional partial homology with a cDNA clone from the plant Arabidopsis thaliana (21) displaying the typical peptide PGRx STEVDRAL (Fig.…”

“…Escherichia coli mutants which lack TAL have not yet been reported, nor has a purification of the enzyme been reported for this organism. TAL-deficient mutants of Saccharomyces cerevisiae accumulated Sed-7-P but showed no auxotrophic traits (27). During the systematic sequencing of the E. coli K-12 genome region from 0 to 2.4 min (35), two open reading frames (ORFs) at 0.2 min (the first one starting at bp 7827) which showed significant amino acid identities (54.4 and 51.9% respectively) to the TAL1-derived sequence from S. cerevisiae were identified (27).…”

“…TAL-deficient mutants of Saccharomyces cerevisiae accumulated Sed-7-P but showed no auxotrophic traits (27). During the systematic sequencing of the E. coli K-12 genome region from 0 to 2.4 min (35), two open reading frames (ORFs) at 0.2 min (the first one starting at bp 7827) which showed significant amino acid identities (54.4 and 51.9% respectively) to the TAL1-derived sequence from S. cerevisiae were identified (27). Later, as a result of corrections in the sequence, a single ORF of 317 amino acids was established with overall similarity to the yeast protein (DDBJ accession number 10483).…”

Human Transaldolase-associated Repetitive Elements Are Transcribed by RNA Polymerase III

“…By contrast, TARE is the likely source of TAL-H and HSAG-1 since it is bounded by TA direct repeats in both loci. The TA direct repeats are not part of TARE or a potentially ancestral transaldolase gene since the TAL-H exon 2-and 3-equivalent segments are flanked by dissimilar G(C/T)T dinucleotides in the yeast (42) and A(C/C)T dinucleotides in E. coli (43), respectively. Presence of identical dinucleotide repeats at four strategic locations is a statistically significant finding (p ϭ 0.0002).…”