Prediction of bacterial proteins carrying a nuclear localization signal and nuclear targeting of HsdM from Klebsiella pneumoniae.
Nuclear targeting of bacterial proteins is an emerging pathogenic mechanism whereby bacterial proteins can interact with nuclear molecules and alter the physiology of host cells. The fully sequenced bacterial genome can predict proteins that target the nuclei of host cells based on the presence of nuclear localization signal (NLS). In the present study, we predicted bacterial proteins with the NLS sequences from Klebsiella pneumoniae by bioinformatic analysis, and 13 proteins were identified as carrying putative NLS sequences. Among them, HsdM, a subunit of KpnAl that is a type I restriction-modification system found in K. pneumoniae, was selected for the experimental proof of nuclear targeting in host cells. HsdM carried the NLS sequences, (7)KKAKAKK(13), in the N-terminus. A transient expression of HsdM-EGFP in COS-1 cells exhibited exclusively a nuclear localization of the fusion proteins, whereas the fusion proteins of HsdM with substitutions in residues lysine to alanine in the NLS sequences, (7)AAAKAAA(13), were localized in the cytoplasm. HsdM was co-localized with importin o in the nuclei of host cells. Recombinant HsdM alone methylated the eukaryotic DNA in vitro assay. Although HsdM tested in this study has not been considered to be a virulence factor, the prediction of NLS motifs from the full sequenced genome of bacteria extends our knowledge of functional genomics to understand subcellular targeting of bacterial proteins.
Department of Microbiology, Kyungpook National University School of Medicine, Daegu, Republic of Korea.
Je Chul
JC
Lee
Dong Sun
DS
Kim
Dong Chan
DC
Moon
Jung-Hwa
JH
Lee
Mi Jin
MJ
Kim
Su Man
SM
Lee
Yong Seok
YS
Lee
Se-Won
SW
Kang
Eun Jung
EJ
Lee
Sang Sun
SS
Kang
Eunpyo
E
Lee
Sung Hee
SH
Hyun
D001426:Bacterial Proteins / Q000032:analysis / Q000235:genetics*; D002467:Cell Nucleus / Q000737:chemistry*; D019295:Computational Biology / Q000379:methods; D015280:DNA Restriction-Modification Enzymes / Q000032:analysis* / Q000235:genetics; D005798:Genes, Bacterial; D017930:Genes, Reporter; D016680:Genome, Bacterial; D049452:Green Fluorescent Proteins / Q000032:analysis / Q000235:genetics; D006801:Humans; D028884:Karyopherins / Q000032:analysis; D007711:Klebsiella pneumoniae / Q000235:genetics* / Q000472:pathogenicity*; D019913:Nuclear Localization Signals; D011993:Recombinant Fusion Proteins / Q000032:analysis / Q000235:genetics
D001426:Bacterial Proteins; D015280:DNA Restriction-Modification Enzymes; D028884:Karyopherins; D019913:Nuclear Localization Signals; D011993:Recombinant Fusion Proteins; D049452:Green Fluorescent Proteins; C109829:HsdM protein, Bacteria