Undergraduate Research Journal

Molecular Analysis of the Interaction Between Staphylococcus aureus Protein Sbi and Immune System Protein C3d
Wilson Rodriguez
CONCLUSION
The study conducted using AESOP in order to
explore electrostatic properties allowed us to clarify
the residues responsible for function, especially in
Complex 1. We were able to determine similarities
of Sbi to other secreted proteins of S. aureus, such
as Efb-C and Ehp, and provided insight into the
governing forces at each complex site. We have
demonstrated that electrostatics is the driving force
for the interaction between Sbi and C3d within the
binding site of Complex 1, which is also the binding
site for S. aureus proteins Efb-C/Ehp and endogenous
complement receptor CR2. Given that the function
of CR2-C3d association is to augment B cell and
antibody response, we propose the hypothesis that
electrostatic competition between Efb-C/Ehp and
CR2 for C3d binding may a contributing factor for
S. aureus infection or successful immune system
response. On the other hand, formation of Complex
2 may be dominated by van der Waals interactions
or may be a crystallization packing artifact that
forced the two molecules in the vicinity of each
other, but without forming an actual complex.
Crystallization is requirement for the determination
of three dimensional protein structures by X-ray
diffraction. Future work will be focused on testing
this hypothesis, by using molecular dynamics
simulations to elucidate whether the interactions of
Complex 2 are physico-chemically favorable.
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