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ID 14887
file
creator
Bun-ya, Masanori
Maebuchi, Motohiro
Hashimoto, Takeshi
Yokota, Sadaki
Kamiryo, Tatsuyuki
subject
cDNA cloning
3-ketoacyl-CoA thiolase
sterol carrier protein x
sterol carrier protein 2
Caenorhabditis elegans
NDC
Biology
abstract
We cloned a full-length cDNA of the nematode Caenorhabditis elegans that encodes a 44-kDa protein (P-44, 412 residues) similar to sterol carrier protein x (SCPx). Mammalian SCPx is a bipartite protein: its 404-residue N-terminal and 143-residue C-terminal domains are similar to 3-ketoacyl-CoA thiolase and identical to the precursor of sterol carrier protein 2 (SCP2; also termed non-specific lipid-transfer protein), respectively. P-44 has 56(null)equence identity to the thiolase domain of SCx but lacks the SCP2 sequence. Northern blot analysis revealed only a single mRNA species of 1.4 kb, which agrees well with the length of the cDNA (1371 bp), making it improbable that alternative splicing produces an SCPx-like fusion protein. The sequence similarities of P-44 to conventional thiolases are lesser than that to SCPx. Purified recombinant P-44 cleaved long-chain 3-ketoacyl-CoAs (C8-16) in a thiolytic manner by the ping-pong bi-bi reaction mechanism. The inhibition of P-44 by acetyl-CoA was competitive with CoA and non-competitive with 3-ketooctanoyl-CoA. This pattern of inhibition is shared with SCPx but not with conventional 3-ketoacyl-CoA thiolase, which is inhibited uncompetitively with respect to 3-ketoacyl CoA. From these results, we concluded that nematode P-44 and mammalian SCPx constitute a second isoform of thiolase, which we propose to term type-II 3-ketoacyl-CoA thiolase.
journal title
European Journal of Biochemistry
volume
Volume 245
issue
Issue 2
start page
252
end page
259
date of issued
1997
publisher
Federation of European Biochemical Societies
issn
0014-2956
ncid
pubmed id
language
eng
nii type
Journal Article
HU type
Journal Articles
DCMI type
text
text version
author
rights
Copyright (c) 1999 Federation of European Biochemical Societies
department
Graduate School of Integrated Arts and Sciences