Trapping Capacities, Stability and Interaction Intensity of Subunits from Bacterial Ferritin of Azotobacter Vinelandii

Abstract

Bacterial ferritin with purity for the mass spectrometric analysis was prepared by the column chromatography, the electrophoresis and the RP-HPLC in Azotobacter vinelandii. Bacterial ferritin of Azotobacter vinelandii (AVBF) was further identified by both kinetics of iron release and peptide mass fingerprinting (PMF), respectively. Moreover, the interaction Intensity, stability and polymer among subunits in AVBF were further revealed by both MALDI time of flight mass spectrometry and electrophoresis. AVBF can be used to trap organic small molecules such as methylene blue (MB) and the trapping rate is approximately 15.0 +/- 2.0 MB/AVBF, which mdicates that the heme component located at the interface between monomers of the ferritn subunit participates contributes to trap MB. AVBF and liver ferritin of shark (SLF) can directly release its unstable subunits for the mass spectrometric analysis under the 40%-50% condition both acetonitrile and acetone, respectively, but both proteins can not release the subunits for the analysis under the condition of 20%-30% acetone unless both proteins absorb the laser from the mass spectrometer further. It was well known that the interaction intensity among subunits in AVBF was lower than that of SLF. The interaction intensity among protein subunits were tightly connected with the rate of iron release and storage in ferritin.