The secondary structure of the insect defensin A depends on its environment. A circular dichroism study.
Defensin A is an inducible antibacterial protein isolated from the larvae of Phormia terranovae. The conformation of defensin A has been previously determined by two-dimensional 1H-NMR for concentrations in the range of 4-8 mM in water (Bonmatin JM et al (1992) J Biomol NMR 2, 235-256). CD spectroscopic data of defensin A at lower concentrations (10(-5) to 10(-3) M) are reported herein. The ellipticity in the 200-240 nm wavelength range for various solvents varies as follows: acetonitrile < water < methanol < HFIP. The magnitude of theta 222 is strongly dependent on defensin concentration in a buffer solution, suggesting an aggregation process. The helical content of defensin A is maximum at a pH value range (7.5-8) for which the optimum antibacterial activity was observed (Cociancich S et al (1993) J Biol Chem 268, 19239-19245).
Maget-Dana
R
R
Centre de Biophysique Moléculaire (CNRS), Université d'Orléans, France.
Bonmatin
J M
JM
Hetru
C
C
Ptak
M
M
Maurizot
J C
JC
D000097:Acetonitriles; D000595:Amino Acid Sequence; D000818:Animals; D000890:Anti-Infective Agents; D002412:Cations / Q000494:pharmacology; D002942:Circular Dichroism; D023082:Defensins; D006863:Hydrogen-Ion Concentration; D007301:Insect Hormones / Q000737:chemistry*; D007313:Insecta; D000432:Methanol; D008969:Molecular Sequence Data; D017433:Protein Structure, Secondary; D012997:Solvents / Q000737:chemistry; D014867:Water
D000097:Acetonitriles; D000890:Anti-Infective Agents; D002412:Cations; D023082:Defensins; D007301:Insect Hormones; D012997:Solvents; C058181:insect defensin A; D014867:Water; D000432:Methanol; C032159:acetonitrile