title: Molecular dynamics simulations on pars intercerebralis major peptide-C (PMP-C) reveal the role of glycosylation and disulfide bonds in its enhanced structural stability and function.
abstract: Fucosylation of Thr 9 in pars intercerebralis major peptide-C (PMP-C) enhances its structural stability and functional ability as a serine protease inhibitor. In order to understand the role of disulfide bonds and glycosylation on the structure and function of PMP-C, we have carried out multiple explicit solvent molecular dynamics (MD) simulations on fucosylated and non-fucosylated forms of PMP-C, both in the presence and absence of the disulfide bonds. Our simulations revealed that there were no significant structural changes in the native disulfide bonded forms of PMP-C due to fucosylation. On the other hand, the non-fucosylated form of PMP-C without disulfide bonds showed larger deviations from the starting structure than the fucosylated form. However, the structural deviations were restricted to the terminal regions while core β-sheet retained its hydrogen bonded structure even in absence of disulfide bonds as well as fucosylation. Interestingly, fucosylation of disulfide bonded native PMP-C led to a decreased thermal flexibility in the residue stretch 29-32 which is known to interact with the active site of the target proteases. Our analysis revealed that disulfide bonds covalently connect the residue stretch 29-32 to the central β-sheet of PMP-C and using a novel network of side chain interactions and disulfide bonds fucosylation at Thr 9 is altering the flexibility of the stretch 29-32 located at a distal site. Thus, our simulations explain for the first time, how presence of disulfide bonds between conserved cysteines and fucosylation enhance the function of PMP-C as a protease inhibitor.
authors.affiliation: National Institute of Immunology, Aruna Asaf Ali Marg, New Delhi-110067.
authors.forename: Sandeep
authors.initials: S
authors.lastname: Kaushik
authors.forename: Debasisa
authors.initials: D
authors.lastname: Mohanty
authors.forename: Avadhesha
authors.initials: A
authors.lastname: Surolia
mesh_terms: D020134:Catalytic Domain; D047169:Cyclotides / Q000737:chemistry* / Q000378:metabolism*; D003545:Cysteine / Q000737:chemistry; D004220:Disulfides / Q000737:chemistry; D005643:Fucose / Q000737:chemistry; D006031:Glycosylation; D006860:Hydrogen Bonding; D019476:Insect Proteins / Q000737:chemistry* / Q000378:metabolism*; D056004:Molecular Dynamics Simulation; D011487:Protein Conformation; D015842:Serine Proteinase Inhibitors / Q000737:chemistry / Q000378:metabolism
chemical_list: D047169:Cyclotides; D004220:Disulfides; D019476:Insect Proteins; D015842:Serine Proteinase Inhibitors; C072987:PMP-C peptide, insect; D005643:Fucose; D003545:Cysteine