BIOCHEMICAL CHARACTERIZATION OF ANTI-METHICILLIN RESISTANT S. aureus PROTEIN (P-80) FROM MARINE Pseudoalteromonas

The marine Pseudoalteromonas are recognized as major active metabolite producers against different biological targets. These compounds include cyclic peptides, toxic proteins or enzymes, among others. In previous studies, we isolated a protein named P-80 from Pseudoalteromonas sp with antibiotic activity against S. aureus, and proteolytic action. In the present work, we studied properties such as structure and the function of P-80. We performed different assays, including MALDI-TOF mass spectrometry, antibacterial activity by the standard disc diffusion, pH and temperature stability, cytotoxicity in vitro and finally the effect of metal ions and protease inhibitors on antimicrobial activity. The purified P-80 showed a molecular mass of 78.5 kDa as determined by MALDI-TOF mass spectrometry. It was highly active over pH range of 7.0 to 9.2, and remained stable over a pH range of 7.0 to 8.0 although its activity was reduced at pH 9.2 (only 55% was retained). This protein showed quite a good antibacterial activity over a broad temperature range (> 65% of activity is retained between -20 and 70 degrees C). The inhibitor tested such as EDTA, EGTA, PMSF, DTT and TLCK (at 5 mM) had no effect on the antibacterial activity. Whereas Mn-2(+) ions enhanced the antibiotic activity but Zn2+, Fe2+, Mg2+, Ca2+, Cu2+ and Co2+ ions had no effect. In conclusion, the P-80 protein remained 55% and 65 % of its antimicrobial activity against Staphylococcus aureus at pH 9.0 and 70 degrees C respectively, suggesting high stability compared to other marine antibacterial proteins indicating intrinsic features that could enable commercial applications