RKI1/YOR095C Summary Help

Standard Name RKI1 1
Systematic Name YOR095C
Feature Type ORF, Verified
Description Ribose-5-phosphate ketol-isomerase; catalyzes the interconversion of ribose 5-phosphate and ribulose 5-phosphate in the pentose phosphate pathway; participates in pyridoxine biosynthesis (1, 2 and see Summary Paragraph)
Name Description Ribose-5-phosphate Ketol-Isomerase 1
Chromosomal Location
ChrXV:504328 to 503552 | ORF Map | GBrowse
Note: this feature is encoded on the Crick strand.
Gene Ontology Annotations All RKI1 GO evidence and references
  View Computational GO annotations for RKI1
Molecular Function
Manually curated
Biological Process
Manually curated
Cellular Component
Regulators 15 genes
Classical genetics
Large-scale survey
reduction of function
30 total interaction(s) for 27 unique genes/features.
Physical Interactions
  • Affinity Capture-MS: 1
  • Affinity Capture-RNA: 2
  • Co-crystal Structure: 1
  • PCA: 1
  • Reconstituted Complex: 1
  • Two-hybrid: 6

Genetic Interactions
  • Negative Genetic: 10
  • Positive Genetic: 4
  • Synthetic Growth Defect: 1
  • Synthetic Lethality: 3

Expression Summary
Length (a.a.) 258
Molecular Weight (Da) 28,258
Isoelectric Point (pI) 5.77
Phosphorylation PhosphoGRID | PhosphoPep Database
sequence information
ChrXV:504328 to 503552 | ORF Map | GBrowse
Note: this feature is encoded on the Crick strand.
Last Update Coordinates: 2011-02-03 | Sequence: 1996-07-31
Subfeature details
Most Recent Updates
Coordinates Sequence
CDS 1..777 504328..503552 2011-02-03 1996-07-31
Retrieve sequences
Analyze Sequence
S288C only
S288C vs. other species
S288C vs. other strains
External Links All Associated Seq | E.C. | Entrez Gene | Entrez RefSeq Protein | MIPS | Search all NCBI (Entrez) | UniProtKB
Primary SGDIDS000005621

Rki1p is a D-ribose-5-phosphate ketol-isomerase (EC: in the non-oxidative branch of the pentose phosphate pathway (1). In addition to the pentose phosphate pathway, Rki1p is also involved in pyridoxine biosynthesis. Pyridoxine is the major form of vitamin B6 and is a precursor for pyridoxal phosphate, an important coenzyme for amino acid metabolism (2). RKI1 is transcriptionally repressed in response to lithium chloride, and may be transcriptionally regulated in response to stress, as suggested by promoter analysis (3, 1). Active Rki1p is a tetramer and Rki1p is very unstable in crude extracts (2, 1). Rki1p localizes to the nucleus and cytoplasm (4).

rki1 null mutants are inviable, which suggests that Rki1p has an additional essential role other than its role in the non-oxidative part of the pentose-phosphate pathway since defects in genes encoding other enzymes of this part of the pentose phosphate pathway (rpe1 null mutants) are not lethal (2, 1). rki1-[R189K] mutants display a pyridoxine auxotrophy, and Rki1p-[R189K] mutant proteins contain 0.6% of the activity of Rki1p, appear to have an altered 3-dimensional structure, and form dimers instead of tetramers (2).

Rki1p has similarity to the ribose 5-phosphate ketol-isomerases from many prokaryotes and eukaryotes that include: Schizosaccharomyces pombe, Arabidopsis thaliana, Caenorhabditis elegans (B0280.3), Drosophila melanogaster, mouse (RPI) and humans. Mutations in the human homolog RPIA (OMIM) are associated with ribose 5-phosphate isomerase deficiency (OMIM; 2, 5, 1).

Last updated: 2005-12-14 Contact SGD

References cited on this page View Complete Literature Guide for RKI1
1) Miosga T and Zimmermann FK  (1996) Cloning and characterization of the first two genes of the non-oxidative part of the Saccharomyces cerevisiae pentose-phosphate pathway. Curr Genet 30(5):404-9
2) Kondo H, et al.  (2004) Pyridoxine biosynthesis in yeast: participation of ribose 5-phosphate ketol-isomerase. Biochem J 379(Pt 1):65-70
3) Bro C, et al.  (2003) Transcriptional, proteomic, and metabolic responses to lithium in galactose-grown yeast cells. J Biol Chem 278(34):32141-9
4) Huh WK, et al.  (2003) Global analysis of protein localization in budding yeast. Nature 425(6959):686-91
5) Graille M, et al.  (2005) Crystal structure of the S. cerevisiae D-ribose-5-phosphate isomerase: comparison with the archaeal and bacterial enzymes. Biochimie 87(8):763-9