Inactivation of the endoplasmic reticulum protein translocation factor, Sec61p, or its homolog, Ssh1p, does not affect peroxisome biogenesis.
Peroxisomes are single membrane-bound organelles present in virtually all eukaryotes. These organelles participate in several important metabolic processes, and defects in peroxisome function and biogenesis are a significant contributor to human disease. Several models propose that peroxisomes arise from the endoplasmic reticulum (ER) in a process that involves the translocation of "group I" peroxisomal membrane proteins into the ER, the exit of these group I peroxisomal membrane proteins from the ER by vesicle budding, and the formation of nascent peroxisomes from vesicles containing the group I peroxisomal membrane proteins. A central prediction of these models is that the formation of nascent peroxisomes requires protein translocation into the ER. Sec61p is an essential component of the ER translocon, and we show here that loss of Sec61p activity has no effect on peroxisome biogenesis. In addition, loss of the SEC61-related gene, SSH1, also has no effect on peroxisome biogenesis. Although some proteins may enter the ER independently of Sec61p or Ssh1p, none are known, leading us to propose that peroxisome biogenesis may not require protein import into the ER, and by extension, transfer of proteins from the ER to the peroxisome.
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Department of Biological Chemistry, The Johns Hopkins University School of Medicine, Baltimore, MD 21205, USA.
Baumgart
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Gould
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D018528:ATP-Binding Cassette Transporters; D004721:Endoplasmic Reticulum / Q000378:metabolism*; D005656:Fungal Proteins / Q000235:genetics / Q000378:metabolism; D018840:HSP70 Heat-Shock Proteins / Q000378:metabolism*; D008565:Membrane Proteins / Q000235:genetics / Q000378:metabolism*; D026901:Membrane Transport Proteins; D000074401:Peroxins; D000074435:Peroxisome-Targeting Signal 1 Receptor; D020675:Peroxisomes / Q000378:metabolism*; D018160:Receptors, Cytoplasmic and Nuclear / Q000235:genetics / Q000378:metabolism; D000069816:SEC Translocation Channels; D012441:Saccharomyces cerevisiae / Q000235:genetics / Q000378:metabolism; D029701:Saccharomyces cerevisiae Proteins
D018528:ATP-Binding Cassette Transporters; D005656:Fungal Proteins; D018840:HSP70 Heat-Shock Proteins; D008565:Membrane Proteins; D026901:Membrane Transport Proteins; C070895:PEX3 protein, S cerevisiae; D000074401:Peroxins; D000074435:Peroxisome-Targeting Signal 1 Receptor; D018160:Receptors, Cytoplasmic and Nuclear; D000069816:SEC Translocation Channels; C499383:SEC61 protein, S cerevisiae; C406793:SPF1 protein, S cerevisiae; C499381:SSH1 protein, S cerevisiae; D029701:Saccharomyces cerevisiae Proteins