title: Lipid-mediated unfolding of 3β-hydroxysteroid dehydrogenase 2 is essential for steroidogenic activity.
abstract: For inner mitochondrial membrane (IMM) proteins that do not undergo N-terminal cleavage, the activity may occur in the absence of a receptor present in the mitochondrial membrane. One such protein is human 3β-hydroxysteroid dehydrogenase 2 (3βHSD2), the IMM resident protein responsible for catalyzing two key steps in steroid metabolism: the conversion of pregnenolone to progesterone and dehydroepiandrosterone to androstenedione. Conversion requires that 3βHSD2 serve as both a dehydrogenase and an isomerase. The dual functionality of 3βHSD2 results from a conformational change, but the trigger for this change remains unknown. Using fluorescence resonance energy transfer, we found that 3βHSD2 interacted strongly with a mixture of dipalmitoylphosphatidylglycerol (DPPG) and dipalmitoylphosphatidylcholine (DPPC). 3βHSD2 became less stable when incubated with the individual lipids, as indicated by the decrease in thermal denaturation (T(m)) from 42 to 37 °C. DPPG, alone or in combination with DPPC, led to a decrease in α-helical content without an effect on the β-sheet conformation. With the exception of the 20 N-terminal amino acids, mixed vesicles protected 3βHSD2 from trypsin digestion. However, protein incubated with DPPC was only partially protected. The lipid-mediated unfolding completely supports the model in which a cavity forms between the α-helix and β-sheet. As 3βHSD2 lacks a receptor, opening the conformation may activate the protein.
authors: Mercer University School of Medicine and Memorial University Medical Center, Savannah, Georgia 31404, United States.
authors: Maheshinie
authors: M
authors: Rajapaksha
authors: James L
authors: JL
authors: Thomas
authors: Michael
authors: M
authors: Streeter
authors: Manoj
authors: M
authors: Prasad
authors: Randy M
authors: RM
authors: Whittal
authors: John D
authors: JD
authors: Bell
authors: Himangshu S
authors: HS
authors: Bose
mesh_terms: D015060:1,2-Dipalmitoylphosphatidylcholine / Q000378:metabolism*; D000818:Animals; D004795:Enzyme Stability; D006801:Humans; D007527:Isoenzymes / Q000737:chemistry / Q000235:genetics / Q000378:metabolism; D007985:Leydig Cells / Q000378:metabolism; D008297:Male; D051379:Mice; D008928:Mitochondria / Q000378:metabolism; D008958:Models, Molecular; D010715:Phosphatidylglycerols / Q000378:metabolism*; D011284:Pregnenolone / Q000378:metabolism*; D011375:Progesterone Reductase / Q000737:chemistry* / Q000235:genetics / Q000378:metabolism*; D011489:Protein Denaturation; D017433:Protein Structure, Secondary; D058767:Protein Unfolding; D059748:Proteolysis; D011994:Recombinant Proteins / Q000737:chemistry / Q000378:metabolism; D016415:Sequence Alignment; D053835:Unilamellar Liposomes
chemical_list: D007527:Isoenzymes; D010715:Phosphatidylglycerols; D011994:Recombinant Proteins; D053835:Unilamellar Liposomes; D015060:1,2-Dipalmitoylphosphatidylcholine; D011284:Pregnenolone; C533068:3 beta-hydroxysteroid dehydrogenase type II; D011375:Progesterone Reductase; C030345:1,2-dipalmitoylphosphatidylglycerol