Mutations of putP that alter the lithium sensitivity of Salmonella typhimurium

R. S. Myers, S. R. Maloy

Research output: Contribution to journalArticlepeer-review

12 Scopus citations


The putP gene encodes the major proline permease in Salmonella typhimurium that couples transport of proline to the sodium electrochemical gradient. To identify residues involved in the cation binding site, we have isolated putP mutants that confer resistance to lithium during growth on proline. Wild‐type S. typhimurium can grow well on proline as the sole carbon source in media supplemented with NaCl, but grows poorly when LiCl is substituted for NaCl. In contrast to the growth phenotype, proline permease is capable of transporting proline via Na+/proline or Li+/proline symport. Therefore, we selected mutants that grow well on media containing proline as the sole carbon source in the presence of lithium ions. All of the mutants assayed exhibit decreased rates of Li+pro‐line and Na+/proline cotransport relative to wild type. The location of each mutation was determined by deletion mapping: the mutations cluster in two small deletion intervals at the 5′ and 3′ termini of the putP gene. The map positions of these lithium resistance mutations are different from the locations of the previously isolated substrate specificity mutations. These results suggest that Lir mutations may define domains of the protein that fold to form the cation binding site of proline permease.

Original languageEnglish (US)
Pages (from-to)749-755
Number of pages7
JournalMolecular Microbiology
Issue number6
StatePublished - Nov 1988
Externally publishedYes

ASJC Scopus subject areas

  • Microbiology
  • Molecular Biology


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