The Use Of MALDI-TOF Peptide Mass Fingerprinting To Study Proteins From Cyanobacterium Microcystis Aeruginosa PCC7806

We have identified proteins from Microcystis aeruginosa PCC7806 by proteomic methods,especially by Peptide Mass Fingerprinting.The combined analysis by 2-DE and peptide mass fingerprinting strategies were used during this research.Protein samples were extracted,by sonication and TCA/Acetone precipitation, from Microcystis aeruginosa PCC7806 grown on normal BG-11 culture medium.2-D electrophoresis was performed using IPG drystrips of pH 4-7 in the first dimension isoelectric focussing and SDS-PAGE in the second dimension.Proteins were stained by Coomassie or Silver staining prior to tryptic digestion.Trypsin porcine was used to digest our protein samples.Extracted peptides mixed with matrix solution were loaded on the plate and then installed on MALDI-TOF MS machine(BRUKER,ReflexTMâ…¢MALDI-TOF) for further analysis.Spectra obtained from different spots were analyzed in order to identify and remove contaminant picks.After this step known as calibration,pick reports of 168 protein spots were submitted to NCBI/ MASCOT database for identifying matching proteins.The on line searching has been realized by comparing experimental parameters(pI and molecular weight) estimated from the gel picture to theoretical parameters found from on line database.From 168 spots,187 proteins were identified since there are 18 spots containing 2 proteins for each spot.These proteins were grouped into three categories according to the relationship between their origin's taxonomy and the species of our case study Microcystis aeruginosa PCC7806.Of 187 identified proteins,14(7.5%) match to the organism of the case study;98(52.4%) proteins originate from other kind of cyanobacteria and 75(40.1%) proteins are from the species which are not cyanobacteria but chosen by considering other criteria such as pI and molecular weight.The percentage represented in the first group show that the number of matching proteins is still low comparing with the last two groups;this means that other researches still need to be carried out on Microcystis aeruginosa PCC7806.