Three-dimensional structure/function analysis of SCP-2-like2 reveals differences among SCP-2 family members

Abstract

Mosquito sterol carrier protein-2 (AeSCP-2) and sterol carrier protein-2-like2 (AeSCP-2L2) are members of the SCP-2 protein family with similar expression profiles in the mosquito life cycle. In an effort to understand how lipids can be transported by different SCP-2 proteins, the three-dimensional crystal structure of AeSCP-2L2 was solved at 1.7 Å resolution. AeSCP-2L2 forms a dimer and binds three fatty acids, one of which resides in a position within the internal cavity at a right angle to the others. This first report of ligand-bound dimerized protein in the SCP-2 protein family indicates that the family has a much more divergent mode of interaction with ligands than previously reported. The potential function of AeSCP-2L2 was investigated via in vivo incorporation of [ 3 H]cholesterol and [ 3 H]palmitic acid. Overexpression of AeSCP-2L2 in mosquito cells leads to an increased uptake of free fatty acid, whereas knockdown of AeSCP-2L2 in adult females decreases the accumulation of free fatty acid in the fat body from a blood meal. In contrast, overexpression or knockdown of AeSCP-2L2 has no effect on cholesterol uptake. Our results suggest that the main function of AeSCP-2L2 is as a general intracellular fatty acid carrier, as opposed to having a dedicated role in cholesterol transport.-Dyer, D. H., V. Wessely, K. T. Forest, and Q. Lan. Three-dimensional structure/function analysis of SCP-2-like2 reveals differences among SCP-2 family members. J. Lipid Res. 2008. 49: 644-653.

A New Structural Form in the SAM/Metal-Dependent O‑Methyltransferase Family: MycE from the Mycinamicin Biosynthetic Pathway

“…The AD has an α/β structure composed of a four-stranded, mixed β-sheet with a five-helix bundle arranged on one face. A DALI search 13 identified the closest structural matches in the sterol carrier protein 2 (SCP-2) family 14; 15 . The closest structural homolog among the SCP-2 domains 14 , (PDB 2QZT) has just 11% sequence identity and 2.9 Å RMSD with the MycE AD.…”

Unbound DHA causes a high blank value in β‐oxidation assay: a concern for in vitro studies

“…Most data were based on molecular structure aspects and did not address the binding capacity of FA to albumin by reference to biochemical activities, which was in fact the concern of most lipid-related studies. As regards the in vivo situation, a number of intracellular proteins, such as lipoproteins, FA-binding proteins or mosquito sterol carrier protein-2 [19] were shown to exhibit high affinities for FA and to effectively compete with albumin [1,20]. Binding constants of FA to FABPs of various organs and animal species were also observed to strongly differ as the degree of unsaturation [21], but DHA was not assayed in the reported assays.…”

Bioassay guided isolation of mosquito larvicidal compound from acetone leaf extract of Elaeagnus indica Servett Bull and its in-silico study

“…The inhibition of SCPs affects cholesterol uptake and transport and has consequential effects on mosquitos. Sterol carrier protein inhibitors (SCPIs) are new class of insecticides that target the SCP-2, which is partially responsible for cholesterol trafficking in mosquitos (Larson et al, 2008;Lan and Massey, 2004;Blitzer et al, 2005;Kim et al, 2005;Dyer et al, 2008). Moreover, SCP-2 is inessential for survival in vertebrates (Kannenberg et al, 1999;Fuchs et al, 2001).…”