Proteomic Analysis Of Zinc Effects On Streptococcus Pneumoniae

The human pathogen Streptococcus pneumoniae is a commensal of the nasopharynx, but it can become virulent by infecting the lung, middle ear, brain, and bloodstream, causing severe diseases such as pneumonia, otitis media, meningitis, and sepsis. An important metal ion that S. pneumoniae could face is Zn2+, which is present in the human body in concentrations ranging from a fewμM to over 100μM. In the host, Zn2+is of great importance for immunity, as it is necessary for proper functioning of immune cells, and mild Zn2+ deficiency severely affects immune function. Zn2+is crucial for bacterial growth and metabolism as it is the co-factor in many key enzymes. Moreover, Zn2+is involved in bacterial adherence and virulence. This project aims to investigate the molecular basis of the bacterial growth inhibition induced by Zn2+ deficiency and to find out the mechanism of Zn2+effects on S. pnemunoniae virulence.AIM:Establish the 2DE maps of Zn2+regulatory proteins of S. pnemunoniae and investigate the molecular mechanism of Zn2+-regulated growth inhibition of S. pneumoniae.METHOD:2DE-based proteomic approach was used to compare the differences of protein expression in S. pnemunoniae with and without zinc ion.2DE-gel maps were established for the total proteins extracted from the bacteria and the sub-proteome after Zn-IMAC separation, respectively. Proteins with altered expression were identified by MALDI-TOF/TOF mass spectrometry and further characterized based on their molecular functions.RESULT:With the 2DE analysis for the total protein extracts,96 protein spots were found to have different expressions with Zn2+deficiency and 67 unique proteins including 32 down-regulated and 35 up-regulated proteins were identified. These Zn2+regulatory proteins involve in various biological processes including oxidation, protein folding and carbohydrate metabolism. By using Zn-IMAC separation, Zn2+binding proteins in S. pneumoniae were also profiled by 2DE and 10 different protein spots with 7 unique proteins were identified.CONCLUSION:Zn2+deficiency affects the growth of S. pneumoniae. Zn2+regulated proteins can be identified by 2DE-based proteomic technology. Further functional analysis revealed that these Zn2+regulated proteins involve in oxidation, proteins folding and carbohydrate metabolism. These results provide information to help us better understand the molecular basis of the growth and virulence inhibition of S. pneumoniae induced by Zn2+ deficiency.