Xpt

• Description: xanthine phosphoribosyltransferase
  
  

Gene name	xpt
Synonyms
Essential	no
Product	xanthine phosphoribosyltransferase
Function	purine salvage and interconversion
Metabolic function and regulation of this protein in SubtiPathways: Purine salvage, Nucleotides (regulation)
MW, pI	20 kDa, 5.835
Gene length, protein length	582 bp, 194 aa
Immediate neighbours	pbuX, ypwA
Get the DNA and protein sequences (Barbe et al., 2009)
Genetic context This image was kindly provided by SubtiList

The gene

Basic information

• Locus tag: BSU22070

Database entries

• DBTBS entry: [1]

• SubtiList entry: [2]

The protein

Basic information/ Evolution

• Catalyzed reaction/ biological activity: XMP + diphosphate = 5-phospho-alpha-D-ribose 1-diphosphate + xanthine (according to Swiss-Prot)

• Protein family:

• Paralogous protein(s):

Extended information on the protein

• Kinetic information:

• Domains:

• Modification:

• Cofactor(s):

• Effectors of protein activity:

• Interactions:

• Localization: cell membrane (according to Swiss-Prot)

Database entries

• Structure: 1Y0B, 2FXV (complex with GMP), 1Y27 (the riboswitch in complex with guanine)

• UniProt: P42085

• KEGG entry: [3]

• E.C. number: 2.4.2.22

Additional information

• subject to Clp-dependent proteolysis upon glucose starvation PubMed

Expression and regulation

• Operon: xpt-pbuX PubMed

• Sigma factor:

• Regulation:
  • repressed in the presence of purine nucleotides (PurR) PubMed
  • repressed in the presence of adenine or adenosine (PurR) PubMed
  • induced in the absence of guanine (G-box) PubMed

• Regulatory mechanism:
  • PurR: transcription repression PubMed
  • G-box: transcription termination/ antitermination (riboswitch) PubMed1 PubMed2
  • PurR: transcription repression (molecular inducer: PRPP) PubMed

• Additional information: subject to Clp-dependent proteolysis upon glucose starvation PubMed

Biological materials

• Mutant:

• Expression vector:

• lacZ fusion:

• GFP fusion:

• two-hybrid system:

• Antibody:

References

Susan Arent, Anders Kadziola, Sine Larsen, Jan Neuhard, Kaj Frank Jensen
The extraordinary specificity of xanthine phosphoribosyltransferase from Bacillus subtilis elucidated by reaction kinetics, ligand binding, and crystallography.
Biochemistry: 2006, 45(21);6615-27
[PubMed:16716072] [WorldCat.org] [DOI] (P p)

Per Nygaard, Hans H Saxild
The purine efflux pump PbuE in Bacillus subtilis modulates expression of the PurR and G-box (XptR) regulons by adjusting the purine base pool size.
J Bacteriol: 2005, 187(2);791-4
[PubMed:15629952] [WorldCat.org] [DOI] (P p)

Alexander Serganov, Yu-Ren Yuan, Olga Pikovskaya, Anna Polonskaia, Lucy Malinina, Anh Tuân Phan, Claudia Hobartner, Ronald Micura, Ronald R Breaker, Dinshaw J Patel
Structural basis for discriminative regulation of gene expression by adenine- and guanine-sensing mRNAs.
Chem Biol: 2004, 11(12);1729-41
[PubMed:15610857] [WorldCat.org] [DOI] (P p)

Lars Engholm Johansen, Per Nygaard, Catharina Lassen, Yvonne Agersø, Hans H Saxild
Definition of a second Bacillus subtilis pur regulon comprising the pur and xpt-pbuX operons plus pbuG, nupG (yxjA), and pbuE (ydhL).
J Bacteriol: 2003, 185(17);5200-9
[PubMed:12923093] [WorldCat.org] [DOI] (P p)

H H Saxild, K Brunstedt, K I Nielsen, H Jarmer, P Nygaard
Definition of the Bacillus subtilis PurR operator using genetic and bioinformatic tools and expansion of the PurR regulon with glyA, guaC, pbuG, xpt-pbuX, yqhZ-folD, and pbuO.
J Bacteriol: 2001, 183(21);6175-83
[PubMed:11591660] [WorldCat.org] [DOI] (P p)

L C Christiansen, S Schou, P Nygaard, H H Saxild
Xanthine metabolism in Bacillus subtilis: characterization of the xpt-pbuX operon and evidence for purine- and nitrogen-controlled expression of genes involved in xanthine salvage and catabolism.
J Bacteriol: 1997, 179(8);2540-50
[PubMed:9098051] [WorldCat.org] [DOI] (P p)