Pro-sterol carrier protein-2: role of the N-terminal presequence in structure, function, and peroxisomal targeting. Academic Article uri icon

abstract

  • Although the 20-amino acid presequence present in 15-kDa pro-sterol carrier protein-2 (pro-SCP-2, the precursor of the mature 13-kDa SCP-2) alters the function of SCP-2 in lipid metabolism, the molecular basis for this effect is unresolved. The presequence dramatically altered SCP-2 structure as determined by circular dichroism, mass spectroscopy, and antibody accessibility such that pro-SCP-2 had 3-fold less alpha-helix, 7-fold more beta-structure, 6-fold more reactive C terminus to carboxypeptidase A, 2-fold less binding of anti-SCP-2, and did not enhance sterol transfer from plasma membranes. These differences were not due to protein stability since (i) the same concentration of guanidine hydrochloride was required for 50% unfolding, and (ii) the ligand binding sites displayed the same high affinity (nanomolar K(d) values) in the order: cholesterol straight chain fatty acid > kinked chain fatty acid. Laser scanning confocal microscopy and double immunofluorescence demonstrated that pro-SCP-2 was more efficiently targeted to peroxisomes. Transfection of l-cells or McAR7777 hepatoma cells with cDNA encoding pro-SCP-2 resulted in 45% and 59% of SCP-2, respectively, colocalizing with the peroxisomal marker PMP70. In contrast, l-cells transfected with cDNA encoding SCP-2 exhibited 3-fold lower colocalization of SCP-2 with PMP70. In summary, the data suggest for the first time that the 20-amino acid presequence of pro-SCP-2 alters SCP-2 structure to facilitate peroxisomal targeting mediated by the C-terminal SKL peroxisomal targeting sequence.

published proceedings

  • J Biol Chem

author list (cited authors)

  • Schroeder, F., Frolov, A., Starodub, O., Atshaves, B. B., Russell, W., Petrescu, A., ... Kier, A. B.

complete list of authors

  • Schroeder, F||Frolov, A||Starodub, O||Atshaves, BB||Russell, W||Petrescu, A||Huang, H||Gallegos, AM||McIntosh, A||Tahotna, D||Russell, DH||Billheimer, JT||Baum, CL||Kier, AB

publication date

  • January 1, 2000 11:11 AM