title: Metal ions as cofactors for aggregation of therapeutic peptide salmon calcitonin.
abstract: The effects of multivalent metal ions (Cu(2+)/Zn(2+)/Al(3+)) on the aggregation of salmon calcitonin (sCT)--a therapeutic peptide used worldwide in the treatment of osteoporosis and Paget's disease--have been studied in vitro using NMR (both solution state and solid state), TEM, ThT-fluorescence, and FT-IR spectroscopy. Overall, the various results indicated that the metal-ions-induced conformational transitions in the peptide--mostly toward the β-sheet--facilitate the aggregation of sCT in solution. First, the solution NMR has been used to check the interaction between the peptide and the metal ions. Following this, the formation and characterization of calcitonin aggregates has been performed using TEM, solid state NMR, and FT-IR spectroscopy. The TEM and ThT-fluorescence results revealed that the sCT peptide incubated with Cu(2+) and Zn(2+) metal ions (in aqueous environment) forms globular aggregates, while that with Al(3+) ions forms fibrils. The solid state NMR and FT-IR studies revealed the presence of a substantial amount of β-sheet content in sCT aggregates (formed in the presence of these metal ions) compared to the monomeric sCT, indicating that the metal binding is concomitant with conformational changes. The present study becomes crucial while prescribing this drug peptide under physio-pathological conditions associated with an abnormal accumulation of metal ions (Cu(2+)/Zn(2+)/Al(3+)) in the body (i.e., abnormal metal ion homeostasis).
authors.affiliation: Centre of Biomedical Magnetic Resonance, Sanjay Gandhi Postgraduate Institute of Medical Sciences Campus, Lucknow 226014, India.
authors.forename: Neeraj
authors.initials: N
authors.lastname: Rastogi
authors.forename: Kalyan
authors.initials: K
authors.lastname: Mitra
authors.forename: Dinesh
authors.initials: D
authors.lastname: Kumar
authors.forename: Raja
authors.initials: R
authors.lastname: Roy
mesh_terms: D000535:Aluminum / Q000378:metabolism*; D000595:Amino Acid Sequence; D050071:Bone Density Conservation Agents / Q000737:chemistry / Q000378:metabolism*; D002116:Calcitonin / Q000737:chemistry / Q000378:metabolism*; D002412:Cations / Q000378:metabolism; D003300:Copper / Q000378:metabolism*; D006801:Humans; D008969:Molecular Sequence Data; D019906:Nuclear Magnetic Resonance, Biomolecular; D010001:Osteitis Deformans / Q000188:drug therapy; D010024:Osteoporosis / Q000188:drug therapy; D017433:Protein Structure, Secondary; D017550:Spectroscopy, Fourier Transform Infrared; D015032:Zinc / Q000378:metabolism*
chemical_list: D050071:Bone Density Conservation Agents; D002412:Cations; D003300:Copper; C028815:salmon calcitonin; D002116:Calcitonin; D000535:Aluminum; D015032:Zinc