The cytokines form a family of relatively small, secreted signaling molecules:

Contain about 160–200 AA

4 long, conserved α helices

Control growth and differentiation

TLS Online TPP Program

#Id: 1628

#Unit 4. Cell Communication and Cell Signaling

(C1s)2 are serine proteases, cleaves C4 and C2  has the same functions as Masp-1 and Masp-2.

TLS Online TPP Program

#Id: 1629

#Unit 4. Cell Communication and Cell Signaling

Alternative tickover pathway is initiated when C3 hydrolysed its internal thioester bond, yielding the molecule C3(H2O), in the presence of serum Mg2 binds another serum protein, factor B.

TLS Online TPP Program

#Id: 1630

#Unit 4. Cell Communication and Cell Signaling

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.

TLS Online TPP Program

#Id: 1631

#Unit 4. Cell Communication and Cell Signaling

C5b67 complexes can insert into the membrane of nearby cells and mediate “innocent bystander” lysis.

TLS Online TPP Program

#Id: 1632

#Unit 4. Cell Communication and Cell Signaling

C5b, C6 and C7 complex undergoes a conformational change that exposes hydrophobic regions on the surface of the C7 component capable of inserting into the interior of the microbial membrane.

TLS Online TPP Program

#Id: 1633

#Unit 4. Cell Communication and Cell Signaling

C8 having two peptide chains: C8β and C8αϒ. Binding of C8β with C5b67 complex causes conformational change in the C8 dimer such that hydrophobic domain of C8αϒ can insert into the interior of the phospholipid membrane.