Complement Regulator-Acquiring Surface Protein: Difference between revisions

In nature, BbCRASP-1 exists as a homodimer bound to the spirochete's surface (Cordes et al. 2005). Researchers confirmed this by viewing the presence of pieces of the dimer in solution (Cordes et al. 2005). They viewed the results through analytical ultracentrifugation and saw that dimeric crystals formed. If its dimeric state is threatened, BbCRASP-1 would not be able to function.  

Sequences of high conservation in the C-terminal regions of the protein’s monomers, <scene name='SB2013_L01gr6/C-terminus/1'>residues 241 to 250</scene> , were of interest as a potential binding site (Cordes F et al. 2005). Previous studies showed that deletion of these sites caused a complete inability of BbCRASP-1 to bind FH and FHL-1 regulators (Kraiczy P et al. 2004). Scientists determined whether the role of the C-terminus region was in maintaining structure or directly functioning as a binding site by mutating <scene name='SB2013_L01gr6/Leucine_246/1'>leucine 246</scene> in the C-terminus region of the dimer to aspartate (Cordes F et al. 2005). This new polar molecule disrupted the hydrophobic interactions in the core of the C-terminal region and caused the entire structure to aggregate as functionally inert mutants.  Both the C-terminally truncated and mutated BbCRASP-1 proteins lost their ability to dimerize, inhibiting them from binding to their host’s regulatory factors. It was then concluded that the C-terminus is a structurally sensitive region rather than a direct binding site (Cordes 2005). The C-terminus aids in the stabilization of the dimer by holding the <scene name='SB2013_L01gr6/Monomers/1'>two monomers</scene> in place. The C-terminal of one monomer lies against the <scene name='SB2013_L01gr6/N-terminal_helix/1'>N-terminal half of the helix</scene> of the other and keeps the structure together (Cordes F et al. 2005).