title: The prosegment catalyzes native folding of Plasmodium falciparum plasmepsin II.
abstract: Plasmepsin II is a malarial pepsin-like aspartic protease produced as a zymogen containing an N-terminal prosegment domain that is removed during activation. Despite structural similarities between active plasmepsin II and pepsin, their prosegments adopt different conformations in the respective zymogens. In contrast to pepsinogen, the proplasmepsin II prosegment is 80 residues longer, contains a transmembrane region and is non-essential for recombinant expression in an active form, thus calling into question the prosegment's precise function. The present study examines the role of the prosegment in the folding mechanism of plasmepsin II. Both a shorter (residues 77-124) and a longer (residues 65-124) prosegment catalyze plasmepsin II folding at rates more than four orders of magnitude faster compared to folding without prosegment. Native plasmepsin II is kinetically trapped and requires the prosegment both to catalyze folding and to shift the folding equilibrium towards the native conformation. Thus, despite low sequence identity and distinct zymogen conformations, the folding landscapes of plasmepsin II and pepsin, both with and without prosegment, are qualitatively identical. These results imply a conserved and unusual feature of the pepsin-like protease topology that necessitates prosegment-assisted folding.
authors.affiliation: Department of Food Science, Faculty of Food Science and Technology, Universiti Putra Malaysia, 43400 UPM Serdang, Selangor, DE, Malaysia.
authors.forename: Ahmad Haniff
authors.initials: AH
authors.lastname: Jaafar
authors.affiliation: Department of Molecular and Cellular Biology, College of Biological Science, University of Guelph, Guelph, ON N1G 2W1, Canada.
authors.forename: Huogen
authors.initials: H
authors.lastname: Xiao
authors.affiliation: Department of Food Science & Technology, College of Agricultural and Environmental Sciences, University of Georgia, 100 Cedar Street, Athens, GA 30602, United States.
authors.forename: Derek R
authors.initials: DR
authors.lastname: Dee
authors.affiliation: Department of Food Science, Ontario Agricultural College, University of Guelph, Guelph, ON N1G 2W1, Canada.
authors.forename: Brian C
authors.initials: BC
authors.lastname: Bryksa
authors.affiliation: Department of Biosciences and Bioengineering, Indian Institute of Technology Bombay, Powai, Mumbai 400076, India.
authors.forename: Prasenjit
authors.initials: P
authors.lastname: Bhaumik
authors.affiliation: Faculty of Land and Food Systems, University of British Columbia, MacMillan Building, 2357 Main Mall, Vancouver, BC V6T 1Z4, Canada. Electronic address: rickey.yada@ubc.ca.
authors.forename: Rickey Y
authors.initials: RY
authors.lastname: Yada
mesh_terms: D016282:Aspartic Acid Endopeptidases / Q000378:metabolism*; D002384:Catalysis; D004792:Enzyme Precursors / Q000378:metabolism; D007700:Kinetics; D010434:Pepsin A / Q000378:metabolism; D010435:Pepsinogens / Q000378:metabolism; D010963:Plasmodium falciparum / Q000378:metabolism*; D000072417:Protein Domains; D017510:Protein Folding; D015800:Protozoan Proteins / Q000378:metabolism*
chemical_list: D004792:Enzyme Precursors; D010435:Pepsinogens; D015800:Protozoan Proteins; D016282:Aspartic Acid Endopeptidases; C116755:proplasmepsin II; D010434:Pepsin A; C100637:plasmepsin II
keywords: Aspartic protease; Foldase; Kinetic stability; Plasmepsin II; Protein folding