Bacteria cleavage factors

Activation of either pathway of complement results in the cleavage of C3 to C3b and C3a. The latter is released into the circulation and acts as an anaphylatoxin and a chemotaxin. C3b, with its activated thiol ester, binds to membranes and then activates the subsequent factors in the membrane-attack complex. C3b also acts as an opsonin, binding to receptors on phagocytic cells and resulting in the ingestion of bacteria, viruses, and other foreign particles by these cells. 

Much less is known about termination of transcription in eukaryotes than in bacteria. Once transcribed, specific termination sequences of mRNA are bound by protein complexes (such as CPSF cleavage and poly(A)denylation specificity factor, and CstF cleavage stimulation factor) that process cleavage of the message and subsequent poly(A)denylation. RNA polymerase continues transcription for up to several hundred nucleotides before dissociating from the DNA. 

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