High impact information on SOR1

• Cloning of the mutated gene revealed that rsr4-1 carries a point mutation in a member of the PDX1/SOR1/SNZ (for Pyridoxine biosynthesis protein 1/Singlet oxygen resistant 1/Snooze) family that leads to reduced vitamin B6 content [1].
• This has allowed construction of a model of sorbitol dehydrogenase that provides explanations why sorbitol is not a substrate for alcohol dehydrogenase, why ethanol is not a substrate for sorbitol dehydrogenase, and what determines its specificity for polyols [2].
• The open reading frame YLR070c of Saccharomyces cerevisiae has high sequence similarity to S. cerevisiae sorbitol dehydrogenase and to xylitol dehydrogenase of Pichia stipitis [3].
• A new inducible yeast expression vector, pXS7, was constructed by using the promoter and terminator sequences from the Saccharomyces cerevisiae SOR1 gene, which codes for the sorbitol dehydrogenase protein [4].
• The identification of a sorbitol-induced sorbitol dehydrogenase (SDH) activity from Saccharomyces cerevisiae is described [5].

Biological context of SOR1

• Yeast transformants containing the cloned gene carried on a multicopy plasmid express high levels of SDH1 only when grown on sorbitol, suggesting that the cloned gene contains both regulatory and coding sequences [5].
• The SDH1 structural gene was isolated from a lambda gt11 yeast genomic library using an antibody to a 40-kDa protein induced in yeast cells growing in medium containing sorbitol [5].
• Homozygous mdh and sdh1 diploids are unable to sporulate [6].
• The amino acid sequence of a large segment of the N-terminal part of a liver sorbitol dehydrogenase is now determined and shown to be strictly homologous with the long alcohol dehydrogenases [7].
• Proline and glycine residues suggest largely similar conformations between N-terminal parts of sorbitol dehydrogenase and "long" alcohol dehydrogenases, cysteine and histidine residues suggest a conserved zinc atom at the active site, and other residues correlate with structures of special importance [7].

Associations of SOR1 with chemical compounds

• Much of a loop structure is missing, like in mammalian sorbitol and prokaryotic threonine dehydrogenases, many additional differences occur, and relationships are closest with the sorbitol dehydrogenase, the equivalence of which in P. stipitis may actually be the xylitol dehydrogenase [8].
• Properties of sorbitol dehydrogenase and characterization of a reactive cysteine residue reveal unexpected similarities to alcohol dehydrogenases [9].
• 9. The former pKa value probably represents ionization of an imidazole group and the latter the zinc/water ionization in SDH [10].
• 43 residues (11%) are common to all three enzymes and include a heavy over-representation of glycine (half of all glycine residues in sorbitol dehydrogenase), showing the importance of space restrictions in protein structures [11].
• Affinity labelling of sorbitol dehydrogenase from sheep liver with alpha-bromo-beta-(5-imidazolyl)propionic acid [10].

Analytical, diagnostic and therapeutic context of SOR1

• Cloning and sequence determination of the gene encoding sorbitol dehydrogenase from Saccharomyces cerevisiae [5].
• Sorbitol dehydrogenase was characterized as a homogeneous protein on affinity chromatography and ion-exchange chromatography [9].

References