THE SECONDARY STRUCTURE OF THE INSECT DEFENSIN A DEPENDS ON ITS ENVIRONMENT - A CIRCULAR DICHROISM STUDY

摘要

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(1)H-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 < HFLP. 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). [References: 8]