A cold-sensitive Listeria monocytogenes mutant has a transposon insertion in a gene encoding a putative membrane protein and shows altered (p)ppGpp levels.
A cold-sensitive Listeria monocytogenes mutant designated cld-14 was obtained by transposon Tn917 mutagenesis. The gene interrupted by Tn917 in cld-14 was the L. monocytogenes LMOf2365_1485 homolog, which exhibits 45.7% homology to the Bacillus subtilis yqfF locus. LMOf2365_1485, here designated pgpH, encodes a putative integral membrane protein with a predicted molecular mass of 81 kDa. PgpH is predicted to contain a conserved N-terminal signal peptide sequence, seven transmembrane helices, and a hydrophilic C terminus, which likely extends into the cytosol. The Tn917 insertion in pgpH is predicted to result in production of a premature polypeptide truncated at the fifth transmembrane domain. The C terminus of PgpH, which is probably absent in cld-14, contains a highly conserved HD domain that belongs to a metal-dependent phosphohydrolase family. Strain cld-14 accumulated higher levels of (p)ppGpp than the wild type accumulated, indicating that the function of PgpH may be to adjust cellular (p)ppGpp levels during low-temperature growth. The cld-14pgpH(+) complemented strain was able to grow at a low temperature, like the parent strain, providing direct evidence that the activity of PgpH is important in low-temperature adaptation. Because of its predicted membrane location, PgpH may play a critical role in sensing the environmental temperature and altering cellular (p)ppGpp levels to allow the organism to adapt to low temperatures.
Liu
Siqing
S
Bioproducts and Biocatalysis Research Unit, National Center for Agricultural Utilization Research, Agricultural Research Service, U.S. Department of Agriculture, Peoria, Illinois 61790-4120, USA.
Bayles
Darrell O
DO
Mason
Tricia M
TM
Wilkinson
Brian J
BJ
D001426:Bacterial Proteins / Q000235:genetics; D001483:Base Sequence; D003080:Cold Temperature; D004251:DNA Transposable Elements / Q000235:genetics*; D005798:Genes, Bacterial; D006159:Guanosine Tetraphosphate / Q000378:metabolism*; D008089:Listeria monocytogenes / Q000235:genetics* / Q000254:growth & development / Q000378:metabolism; D008565:Membrane Proteins / Q000235:genetics*; D016133:Polymerase Chain Reaction
D001426:Bacterial Proteins; D004251:DNA Transposable Elements; D008565:Membrane Proteins; D006159:Guanosine Tetraphosphate