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

Abstract

Bacterial ferritin with purity for analysis of mass spectrometry (MS) in Azotobacter vinelandii was prepared by column chromatography, electrophoresis, and RP-HPLC. Bacterial ferritin of Azotobacter vinelandii (AVBF) was further identified by both kinetics of iron release and peptide mass fingerprinting (PMF), respectively. Moreover, interaction intensity, stability, and polymer in AVBF subunits were revealed by both matrix-assisted laser desorption ionization-time of flight-mass spectrometry (MALDI-TOF MS) and electrophoresis. Bacterial ferritin of Azotobacter vinelandi can be used to trap the small organic molecules such as methylene blue (MB), and the trapping rate is approximately 15.0 ± 2.0 MB/AVBF. It is suggested that heme component located at the interface between subunits or monomers in AVBF participates this process for trapping MB. Bacterial ferritin of Azotobacter vinelandi and liver ferritin of shark (SLF) can directly release its unstable subunits for MS analysis under the conditions of 40%–50% concentration of both acetonitrile and acetone, respectively, but both the proteins cannot release its subunits for MS analysis under the condition of 20%–30% acetonitrile unless both proteins further absorb the laser from the mass spectrometer. It was well known that the interaction intensity among subunits in AVBF was lower than that of SLF. This intensity was strongly connected with the rates of iron release and its storage in ferritin.