Characterization of two endopeptidases encoded by Streptococcus sanguinis

ABSTRACT
Streptococcus sanguinis, typically an oral commensal, can lead to serious human diseases like infective
endocarditis if the organism gains access to the bloodstream. In this project, we are focusing on SepM, a cell
surface endopeptidase found in S. sanguinis. Our earlier work with Streptococcus mutans revealed that SepM
is crucial for antimicrobial peptide (AMP) secretion and dental cries formation. In group-A-streptococci, the
absence of SepM homolog most likely leads to vesicle mediated M-protein secretion, a protein known to evade
immune cells during infection. In S. sanguinis genome, we discovered the presence of two SepM homologs
(instead of one), which is quite unusual for any streptococci. Interestingly, the function of these two SepM
homologs in S. sanguinis are not well understood. Deleting either of the SepM homologs led to auto-aggregation.
Analysis of the secreted proteome using mass spectrometry revealed a distinctive differential presence of
proteins involved in host invasion. Our proposal aims to further investigate the functions of SepM proteins in the
pathophysiology of S. sanguinis. We will identify virulence factors affected by SepM homologs and assess their
impact including using a wax moth larva insect model, acknowledging the significance of S. sanguinis in diverse
human diseases.

Grant Number: 1R21DE034331-01A1
NIH Institute/Center: NIH
Principal Investigator: SASWATI BISWAS