Human small G proteins, ObgH1, and ObgH2, participate in the maintenance of mitochondria and nucleolar architectures.
The Obg subfamily protein is one of the P-loop small G proteins and is highly conserved in many organisms from bacteria to human. Two obg genes, obgH1 and obgH2, exist in the human genome. Both ObgH1 and ObgH2 showed similar GTPase activities (0.014 +/- 0.005 and 0.010 +/- 0.002/min for ObgH1 and ObgH2, respectively) to those of the bacterial Obg proteins and complemented the Obg function in Escherichia coli ribosome maturation, suggesting that the functions of Obg proteins are well conserved through evolution. Immunofluorescence microscopy of HeLa cells revealed that ObgH1 localizes in mitochondria, and ObgH2 in the dense fibrillar compartment region of the nucleolus. Knock-down of ObgH1 by RNAi induced mitochondria elongation, whereas knock-down of ObgH2 resulted in the disorganization of the nucleolar architecture. In conclusion, the two human Obg proteins have similar enzymatic activities that can complement bacterial Obg function, but show different cellular function(s) with different intracellular localizations.
Hirano
Yasuhiro
Y
Graduate School of Biostudies, Kyoto University, Kyoto 606-8502 Japan. hirano@lif.kyoto-u.ac.jp
Ohniwa
Ryosuke L
RL
Wada
Chieko
C
Yoshimura
Shige H
SH
Takeyasu
Kunio
K
D000595:Amino Acid Sequence; D001426:Bacterial Proteins / Q000235:genetics; D001483:Base Sequence; D002466:Cell Nucleolus / Q000378:metabolism*; D017124:Conserved Sequence; D004926:Escherichia coli / Q000235:genetics / Q000378:metabolism; D029968:Escherichia coli Proteins / Q000235:genetics / Q000378:metabolism; D019143:Evolution, Molecular; D019204:GTP-Binding Proteins / Q000235:genetics; D005816:Genetic Complementation Test; D006367:HeLa Cells; D006801:Humans; D008928:Mitochondria / Q000378:metabolism*; D008969:Molecular Sequence Data; D020559:Monomeric GTP-Binding Proteins / Q000037:antagonists & inhibitors / Q000235:genetics / Q000378:metabolism*; D010802:Phylogeny; D034622:RNA Interference; D034741:RNA, Small Interfering / Q000235:genetics; D017386:Sequence Homology, Amino Acid
D001426:Bacterial Proteins; D029968:Escherichia coli Proteins; C090542:Obg GTP-binding protein, Bacteria; D034741:RNA, Small Interfering; D019204:GTP-Binding Proteins; C516954:GTPBP10 protein, human; C516953:MTG2 protein, human; D020559:Monomeric GTP-Binding Proteins