Structural aspects and biological properties of the cathelicidin PMAP-36.
PMAP-36 is a cathelicidin-derived host defence peptide originally deduced by a transcript from pig bone marrow RNA. The expression of the propeptide in leukocytes, and the structure, antimicrobial activity, and mechanism of action of the mature peptide were investigated. The proform is stored as a dimeric precursor of 38 kDa formed by a dimerization site at its C-terminal cysteine residue; it is likely that the mature peptide is dimeric when released. Monomeric and dimeric forms of PMAP-36 were chemically synthesized and their activity compared. Both forms assumed an amphipathic alpha-helical conformation and exhibited a potent and rapid microbicidal activity against a wide spectrum of microorganisms, mediated by their ability to permeabilize the microbial membranes rapidly. A shortened fragment localized the helical region to the N terminus, but showed a significantly lower potency and slower permeabilization kinetics, indicating an important role of the nonhelical C-terminal hydrophobic portion of this molecule. Dimerization modulated the effectiveness of the peptide in terms of killing and permeabilization kinetics, and reduced medium dependence. It allows the molecule to achieve an impressive charge density (+28 in 70 residues), although the significance of this feature with respect to biological activity has yet to be determined.
Scocchi
Marco
M
Department of Biochemistry, Biophysics and Macromolecular Chemistry, University of Trieste, Italy. scocchi@bbcm.units.it
Zelezetsky
Igor
I
Benincasa
Monica
M
Gennaro
Renato
R
Mazzoli
Andrea
A
Tossi
Alessandro
A
D000595:Amino Acid Sequence; D000818:Animals; D000900:Anti-Bacterial Agents / Q000737:chemistry / Q000494:pharmacology; D023181:Antimicrobial Cationic Peptides / Q000737:chemistry* / Q000235:genetics / Q000494:pharmacology*; D019281:Dimerization; D004926:Escherichia coli / Q000187:drug effects / Q000648:ultrastructure; D006461:Hemolysis / Q000187:drug effects; D066298:In Vitro Techniques; D008826:Microbial Sensitivity Tests; D008855:Microscopy, Electron, Scanning; D008969:Molecular Sequence Data; D017434:Protein Structure, Tertiary; D011506:Proteins / Q000737:chemistry* / Q000235:genetics / Q000494:pharmacology*; D013211:Staphylococcus aureus / Q000187:drug effects / Q000648:ultrastructure; D013552:Swine; D054804:Cathelicidins
D000900:Anti-Bacterial Agents; D023181:Antimicrobial Cationic Peptides; C085474:PMAP-36; D011506:Proteins; D054804:Cathelicidins