In-silico Analysis and Homology Modeling of ?-carbonic Anhydrase from Streptococcus Sanguinis, an Opportunistic Pathogen Involved in Subacute Infective Endocarditis

Abstract

Streptococcus sanguinis is one of the leading causes of infective endocarditis (IE) in a susceptible population. Although several virulence factors involved in IE have been identified, the exact mechanism by which S. sanguinis colonizes endocardium remains unclear. In addition to some well-characterized virulence factors, S. sanguinis also contains virulence-associated proteins that are not well characterized. One such protein that is associated with virulence is carbonic anhydrase (CA) that catalyzes the reversible hydration of CO2 to bicarbonate. The goal of this study is to identify and characterize carbonic anhydrase from S. sanguinis. We have identified a ?-CA from S. sanguinis (SsaCanB) using BLAST analysis that shows high homology to other well-studied ?-carbonic anhydrases. SsCanB is an 18.2 kDa protein with no N-terminal signal peptide indicating its cytoplasmic localization. Sequence alignment of S. sanguinis with closely related homologs shows conserved domains typical of ?-CA including residues important for metal coordination and protein-protein interactions. Homology modeling and subsequent structure analysis of SsCanB reveals that both proteins have ?/? fold typical of ?-CA’s. Analysis of the active site of SsaCanB shows conserved residues involved in zinc ion coordination similar to other well-studied ?-CA’s. Furthermore, the catalytic dyad (Asp/Arg) required for the activation of water molecule coordinated with