title: Solution structure of a synthetic lytic peptide: the perforin amino terminus.
abstract: BACKGROUND
  Killer lymphocytes secrete perforin, a 67 kDa protein that initiates T-cell cytolysis following aggregation and pore formation in target membranes. The resulting pores cause a breakdown of the transmembrane osmotic gradient and allow other cytolytic mediators to enter the target cell and initiate apoptosis. The cytolytic domain resides within the first 34 residues of the amino terminus of perforin, with residues 1-19 being sufficient for cytolytic activity.
  
  
  RESULTS
  The solution structure of a 22-residue synthetic peptide (P22), corresponding to the amino terminus of human perforin, has been determined using high resolution nuclear magnetic resonance spectroscopy in the presence and absence of perdeuterated detergent (SDS) micelles. In aqueous solution, P22 exists mainly in a random conformation. However, it adopts a hook-like structure at the carboxyl terminus in the presence of SDS micelles when the positively charged residues cluster to form a turn that provides a binding surface to the negatively charged sulfate headgroups.
  
  
  CONCLUSIONS
  The strong electrostatic interaction between the cationic region of the P22 peptide and the lipid headgroups probably weakens the membrane, facilitating insertion of the relatively neutral/hydrophobic stretch of P22, and is representative of the initial step of the lytic pathway. The structural model described here is probably relevant to understanding the mechanisms of other cationic antimicrobial peptides.
authors.affiliation: Department of Chemistry, Ohio State University, Columbus 43210, USA.
authors.forename: K
authors.initials: K
authors.lastname: Natarajan
authors.forename: J A
authors.initials: JA
authors.lastname: Cowan
mesh_terms: D000595:Amino Acid Sequence; D006801:Humans; D009682:Magnetic Resonance Spectroscopy; D008562:Membrane Glycoproteins / Q000737:chemistry* / Q000378:metabolism; D008823:Micelles; D008969:Molecular Sequence Data; D054353:Perforin; D052899:Pore Forming Cytotoxic Proteins; D011487:Protein Conformation; D017386:Sequence Homology, Amino Acid; D012967:Sodium Dodecyl Sulfate; D012996:Solutions; D013329:Structure-Activity Relationship
chemical_list: D008562:Membrane Glycoproteins; D008823:Micelles; D052899:Pore Forming Cytotoxic Proteins; D012996:Solutions; D054353:Perforin; D012967:Sodium Dodecyl Sulfate