Numerous invertebrate species belonging to several phyla cannot synthesize sterols de novo and rely on a dietary source of the compound. SCPx (sterol carrier protein 2/3-oxoacyl-CoA thiolase) is a protein involved in the trafficking of sterols and oxidation of branched-chain fatty acids. We have isolated SCPx protein from Spodoptera littoralis (cotton leafworm) and have subjected it to limited amino acid sequencing. A reverse-transcriptase PCR-based approach has been used to clone the cDNA (1.9 kb), which encodes a 57 kDa protein. Northern blotting detected two mRNA transcripts, one of 1.9 kb, encoding SCPx, and one of 0.95 kb, presumably encoding SCP2 (sterol carrier protein 2). The former mRNA was highly expressed in midgut and Malpighian tubules during the last larval instar. Furthermore, constitutive expression of the gene was detected in the prothoracic glands, which are the main tissue producing the insect moulting hormone. There was no significant change in the 1.9 kb mRNA in midgut throughout development, but slightly higher expression in the early stages. Conceptual translation of the cDNA and a database search revealed that the gene includes the SCP2 sequence and a putative peroxisomal targeting signal in the C-terminal region. Also a cysteine residue at the putative active site for the 3-oxoacyl-CoA thiolase is conserved. Southern blotting showed that SCPx is likely to be encoded by a single-copy gene. The mRNA expression pattern and the gene structure suggest that SCPx from S. littoralis (a lepidopteran) is evolutionarily closer to that of mammals than to that of dipterans.
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Research Article|
August 10 2004
Characterization of a sterol carrier protein 2/3-oxoacyl-CoA thiolase from the cotton leafworm (Spodoptera littoralis): a lepidopteran mechanism closer to that in mammals than that in dipterans
Hajime TAKEUCHI;
Hajime TAKEUCHI
1
*Cell Regulation and Signalling Division, School of Biological Sciences, University of Liverpool, Biosciences Building, Crown Street, Liverpool, L69 7ZB, U.K.
1To whom correspondence should be addressed (email htake@liv.ac.uk).
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Jian-Hua CHEN;
Jian-Hua CHEN
2
*Cell Regulation and Signalling Division, School of Biological Sciences, University of Liverpool, Biosciences Building, Crown Street, Liverpool, L69 7ZB, U.K.
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John R. JENKINS;
John R. JENKINS
†Department of Medicine, University of Liverpool, The Henry Wellcome Laboratory, Crown Street, Liverpool, L69 3BX, U.K.
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Masanori BUN-YA;
Masanori BUN-YA
‡Faculty of Integrated Arts and Sciences, Hiroshima University, Kagamiyama 1-7-1, Higashi-Hiroshima, 739-8521, Japan
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Philip C. TURNER;
Philip C. TURNER
*Cell Regulation and Signalling Division, School of Biological Sciences, University of Liverpool, Biosciences Building, Crown Street, Liverpool, L69 7ZB, U.K.
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Huw H. REES
Huw H. REES
*Cell Regulation and Signalling Division, School of Biological Sciences, University of Liverpool, Biosciences Building, Crown Street, Liverpool, L69 7ZB, U.K.
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Publisher: Portland Press Ltd
Received:
April 30 2004
Accepted:
May 18 2004
Accepted Manuscript online:
May 18 2004
Online ISSN: 1470-8728
Print ISSN: 0264-6021
The Biochemical Society, London
2004
Biochem J (2004) 382 (1): 93–100.
Article history
Received:
April 30 2004
Accepted:
May 18 2004
Accepted Manuscript online:
May 18 2004
Citation
Hajime TAKEUCHI, Jian-Hua CHEN, John R. JENKINS, Masanori BUN-YA, Philip C. TURNER, Huw H. REES; Characterization of a sterol carrier protein 2/3-oxoacyl-CoA thiolase from the cotton leafworm (Spodoptera littoralis): a lepidopteran mechanism closer to that in mammals than that in dipterans. Biochem J 15 August 2004; 382 (1): 93–100. doi: https://doi.org/10.1042/BJ20040717
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