title: Molecular cloning and characterization of Bombyx mori sterol carrier protein x/sterol carrier protein 2 (SCPx/SCP2) gene.
abstract: Cholesterol transport is a very important process in insect. We have isolated the Bombyx mori sterol carrier protein x (BmSCPx) cDNA and sterol carrier protein 2 (BmSCP2) cDNA: a 1.7 kb clone encoding SCPx, a 3-ketoacyl CoA thiolase, and 0.6 kb clone presumably encoding SCP2, which is thought to be an intracellular lipid transfer protein. Interestingly, the identical gene SCPx/SCP2 encodes the two types of transcripts by alternative splicing mechanism in Bombyx mori. The SCPx mRNA spans two exons in genome, and conceptual translation of the SCPx cDNA encodes a protein of 536 amino acids, which contains a thiolase domain and a SCP2 domain. Whereas the SCP2 mRNA partly lakes the first exon, and the SCP2 is a 146 amino acids containing a SCP2 domain only. Both BmSCPx and BmSCP2 have a putative peroxisomal targeting signal in the C-terminal region. BmSCPx shares 94 and 72% similarity to Spodoptera littoralis SCPx and human SCPx, respectively. RT-PCR analysis reveals that transcripts of BmSCP2 were detected in all tissues analyzed. BmSCPx transcription expressed only in midgut and malpighian tubules. However, the BmSCPx and BmSCP2 express strong in midgut during the last instar larvae. The tissue-specific expression pattern of BmSCPx and BmSCP2 is consistent with a role for these proteins in cholesterol metabolism. The results suggest that SCPx/SCP2 may play a key role in sterol absorption and intracellular carrier in silkworm.
authors.affiliation: Key Sericultural Laboratory of Agricultural Ministry, Southwest University, Chongqing 400715, People's Republic of China.
authors.forename: Jing
authors.initials: J
authors.lastname: Gong
authors.forename: Yong
authors.initials: Y
authors.lastname: Hou
authors.forename: Xing-Fu
authors.initials: XF
authors.lastname: Zha
authors.forename: Cheng
authors.initials: C
authors.lastname: Lu
authors.forename: Yong
authors.initials: Y
authors.lastname: Zhu
authors.forename: Qing-You
authors.initials: QY
authors.lastname: Xia
mesh_terms: D000595:Amino Acid Sequence; D000818:Animals; D001483:Base Sequence; D012831:Bombyx / Q000235:genetics*; D002352:Carrier Proteins / Q000737:chemistry / Q000235:genetics* / Q000378:metabolism; D002784:Cholesterol / Q000378:metabolism*; D008969:Molecular Sequence Data
chemical_list: D002352:Carrier Proteins; C072087:sterol carrier proteins; D002784:Cholesterol