Pertussis toxin, produced by Bordetella pertussis, catalyzes ADP-ribosylation of the  subunit of Gαi, preventing GDP-GTP exchange and blocking inhibition of adenylyl cyclase.

TLS Online TPP Program

#Id: 1930

#Unit 4. Cell Communication and Cell Signaling

The Alternative Protease-Activated Pathway

Thrombin, could cleave the complement components C3 and C5.

TLS Online TPP Program

#Id: 1931

#Unit 4. Cell Communication and Cell Signaling

When blood platelets are activated during a clotting reaction, they release high concentrations of ATP and Ca2+ along with serine/threonine kinases. Phosphorylated C3b is less susceptible to proteolytic degradation than its unphosphorylated form

TLS Online TPP Program

#Id: 1932

#Unit 4. Cell Communication and Cell Signaling

The Three Complement Pathways Converge at the Formation of the C5 Convertase. 

TLS Online TPP Program

#Id: 1933

#Unit 4. Cell Communication and Cell Signaling

C5 Initiates the Generation of the MAC

TLS Online TPP Program

#Id: 1934

#Unit 4. Cell Communication and Cell Signaling

C8 is made up of two peptide chains: C8β and C8αϒ. 

Binding of C8β to the C5b67 complex induces a conformational change in the C8 dimer such that the hydrophobic domain of C8αϒ can insert into the interior of the phospholipid membrane. 

TLS Online TPP Program

#Id: 1935

#Unit 4. Cell Communication and Cell Signaling

The C5b component is extremely labile, is not covalently bound to the membrane like C3b and C4b, and is rapidly inactivated unless it is stabilized by the binding of C6.