Biochemical Characterization of a Bacterial Adhesin Protein, SraP

Infective Endocarditis (IE) is a life threatening infection of the heart valves that can be caused by Gram positive bacteria, including is Staphylococcus aureus. Cell surface bacterial adhesins mediates the binding of S.aureus to platelets, which is required for pathogenesis. One of the S. aureus adhesins involved in IE is called Serine-Rich Adhesin for platelets (SraP).  This glycoprotein contains an atypical N-terminal signal sequence and two serine rich repeat regions separated by a non repeat region.  The structural basis for selectivity of bacterial pathogen adhesins is limited.  Determining the crystal structure of SraP through X-ray crystallography will contribute to the knowledge of the binding site architecture of SraP.  These details may aide in the proposal of a mechanism/potential therapeutic against Infective Endocarditis.  The goal was to obtain pure SraP by using an established protocol with two different DNA constructs and identify new crystallization conditions.  To investigate the structural details of SraP, recombinant GST-SraP_150-758 and GST-SraP_90-758 fusion protein was overexpressed in Escherichia coli and purified by affinity and size exclusion chromatography.  Challenges occurred in the expression of SraP construct_150-758 and purification of SraP_90-758.