Mutations in yhiT enable utilization of exogenous pyrimidine intermediates in Salmonella enterica serovar Typhimurium

Microbiology (Reading). 2007 Aug;153(Pt 8):2472-2482. doi: 10.1099/mic.0.2007/007583-0.


Mutants capable of utilizing the pyrimidine biosynthetic intermediates carbamoylaspartate and dihydroorotate for growth were derived from pyrimidine auxotrophs of Salmonella enterica serovar Typhimurium LT2. The gain-of-function phenotypes both resulted from mutations in a single gene, yhiT, the third gene of a putative four-gene operon, yhiVUTS, for which there is no homologous region in Escherichia coli. Notably, when a mutant yhiT allele was transferred to a pyrimidine-requiring E. coli strain, the transformant was then capable of using carbamoylaspartate or dihydrorotate as a pyrimidine source. The operon arrangement of the yhiVUTS genes was supported by genetic analyses and studies employing RT-PCR, coupled to the determination of the transcriptional start site using 5'-random amplification of cDNA ends (RACE). Computer-generated predictions indicated that YhiT is an integral membrane protein with 12 putative transmembrane domains typical of bacterial transport proteins. Competition experiments showed that mutant YhiT interacts with the C4-dicarboxylates succinate and malate, as well as the amino acids aspartate and asparagine. The native function of wild-type YhiT remains undetermined, but the collective results are consistent with a role as a general transporter of C4-dicarboxylates and other compounds with a similar basic structure.

Publication types

  • Research Support, Non-U.S. Gov't

MeSH terms

  • Amino Acid Sequence
  • Asparagine / metabolism
  • Aspartic Acid / analogs & derivatives*
  • Aspartic Acid / metabolism
  • Bacterial Proteins / genetics*
  • Base Sequence
  • Carrier Proteins / genetics*
  • Cloning, Molecular
  • Escherichia coli / genetics
  • Escherichia coli / metabolism
  • Genes, Bacterial
  • Malates / metabolism
  • Membrane Proteins / genetics*
  • Molecular Sequence Data
  • Mutation*
  • Operon
  • Orotic Acid / analogs & derivatives*
  • Orotic Acid / metabolism
  • RNA, Messenger / biosynthesis
  • Reverse Transcriptase Polymerase Chain Reaction
  • Salmonella typhimurium / genetics
  • Salmonella typhimurium / metabolism*
  • Succinic Acid / metabolism
  • Transcription Initiation Site


  • Bacterial Proteins
  • Carrier Proteins
  • Malates
  • Membrane Proteins
  • RNA, Messenger
  • 4,5-dihydroorotic acid
  • Aspartic Acid
  • Orotic Acid
  • Asparagine
  • malic acid
  • Succinic Acid
  • ureidosuccinic acid