1995 Fiscal Year Final Research Report Summary
A novel molecular chaperone-like protein found in yeast peroxisomes
| Project/Area Number |
05454072
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| Research Category |
Grant-in-Aid for General Scientific Research (B)
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| Allocation Type | Single-year Grants |
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| Research Field |
応用微生物学・応用生物化学
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| Research Institution | HIROSHIMA UNIVERSITY |
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Principal Investigator |
KAMIRYO Tatsuyuki Hiroshima U., F.Integ.Arts & Sci., Prof., 総合科学部, 教授 (50025649)
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| Co-Investigator(Kenkyū-buntansha) |
BUN-YA Masanori Hiroshima U., F.Integ.Arts & Sci., Assist., 総合科学部, 助手 (40243521)
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| Project Period (FY) |
1993 – 1995
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| Keywords | Peroxisomes / Acyl-CoA Oxidase / Sterol Carrier Protein 2 / Stress Ptotein / Molecular Chaperone |
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| Research Abstract |
This project aimed at understanding the physiological role of a yeast homologue of nonspecific lipid-transfer protein (nsLTP or SCP2) , which we found in peroxisomes of the yeast Candida tropicalis and named PXO-18. No molecular chaperone or stress protein has been found in peroxisomes thus far. Our results suggest that PXP-18 should be a possible candidate for it.
1) PXP-18 was shown to be present predominantly in the matrix of peroxisomes by means of immunoeLectron microscopy, subcellular fractionation, and by importing the protein. PXP-18 protected peroxisomal acyl-CoA oxidase (ACO) from thermal inactivation at 48ﾟC or 70ﾟC.When heated at 70ﾟC for 15 min, PXP-18 and ACO subunit formed a nearstoichiometric complex, independent of their initial ratio. Free ACO was released from the isolated complex spontaneously at 30ﾟC.PXP-18 changed its secondary structure reversibly at 70ﾟC,and formed homodimers in a manner dependent on time and temperature. The dimeric PXP-18 may bind to octameric ACOs denatured partially to form the nearstoichiometric complex, preventing their further denaturation.
2) A cDNA clone of the nematode Caenorhabditis elegans revealed a protein (TLP) that is highly similar to thiolase-SCP2 but lacks SCP2 moiety ; thiolase-SCP2 is encoded by the longer mRNA from the mammalian SCP2 gene and shows 3-oxoacyl-CoA thiolase activity. TLP and PXP-18 seems to represent the evolutionary origins of thiolase-SCP2. PXP-18 may facilitate the incorporation of the fused thiolase into a putative beta-oxidation complex, as ubiquitin does. Ubiquitin, a stress protein, is also expressed as a fused form with ribosomal proteins and facilitates their incorporation into ribosomes.
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