Identification of an Arabidopsis unknown small membrane protein targeted to mitochondria, chloroplasts, and peroxisomes.
In a functional genomic screen performed by combining an Arabidopsis-yellow fluorescent protein (YFP)-fused complementary DNA (cDNA) library, rat fibroblasts as host and automatic microscopy, we found a short protein with a predictable trans-membrane domain encoded on chromosome 2. In rat fibroblasts, its pattern of distribution was to various organelle-like structures. From the databases, we learned that it has another family member in Arabidopsis and homologs in several other plants, Chlamydomonas and fungi, with a highly conserved N-terminal region. We named this protein from Arabidopsis short membrane protein (SMP) 2. No SMP homologs were found in mammalian sequence databases. When the full-length cDNAs of SMP2 was fused to YFP under the 35S promoter, comparable distribution was observed in Nicotiana benthamiana leaves, suggesting an unknown, evolutionarily conserved localization signal. Similar localization was observed when SMP2 was expressed in N. benthamiana leaves under the control of its own 5' regulatory sequences. Colocalization studies with green fluorescent protein and red fluorescent protein chimeras revealed its colocalization with chloroplasts, peroxisomes, and mitochondria. No localization of SMP2 was observed in the Golgi. Immunostaining with specific antibodies corroborated the SMP2 localization to the three organelles.
Abu-Abied
Mohamad
M
The Department of Ornamental Horticulture, The Institute of Plant Sciences, The Volcani Center, P.O. Box 6, Bet-Dagan, 50250, Israel.
Avisar
Dror
D
Belausov
Eduard
E
Holdengreber
Vered
V
Kam
Zvi
Z
Sadot
Einat
E
D000595:Amino Acid Sequence; D000818:Animals; D029681:Arabidopsis Proteins / Q000235:genetics / Q000378:metabolism*; D015153:Blotting, Western; D002736:Chloroplasts / Q000378:metabolism*; D049452:Green Fluorescent Proteins / Q000235:genetics / Q000378:metabolism; D008853:Microscopy; D008928:Mitochondria / Q000378:metabolism*; D008969:Molecular Sequence Data; D020675:Peroxisomes / Q000378:metabolism*; D000072260:RNA Splicing Factors; D051381:Rats; D011993:Recombinant Fusion Proteins / Q000235:genetics / Q000378:metabolism; D017386:Sequence Homology, Amino Acid; D014157:Transcription Factors / Q000235:genetics / Q000378:metabolism*
D029681:Arabidopsis Proteins; D000072260:RNA Splicing Factors; D011993:Recombinant Fusion Proteins; C507064:SMP1 protein, Arabidopsis; C507063:SMP2 protein, Arabidopsis; D014157:Transcription Factors; D049452:Green Fluorescent Proteins