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.
Lee
Je Chul
JC
Department of Microbiology, Kyungpook National University School of Medicine, Daegu, Republic of Korea.
Kim
Dong Sun
DS
Moon
Dong Chan
DC
Lee
Jung-Hwa
JH
Kim
Mi Jin
MJ
Lee
Su Man
SM
Lee
Yong Seok
YS
Kang
Se-Won
SW
Lee
Eun Jung
EJ
Kang
Sang Sun
SS
Lee
Eunpyo
E
Hyun
Sung Hee
SH
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