protein secretion system??

[Tammy Brackett & Jean Cardinale]

Jongmin-Nam wrote:
> 
> Could anyone tell me what is type 1 and type 2 protein secretion systems?
> I cannot define these systems clearly.
> help me.
> 
> thank you.


Type 1 systems are generally SecA dependent systems which direct nascent
peptides to the cytoplasmic membrane where they are extruded into the
periplasm and beyond.  There is a concensus sequence at the N-terminus
of the new protein which serves as a signal to target the protein for
secretion.

Type 2 systems also serve to target proteins out of the cytoplasm,
however proteins which contain a type two signal end up with a lipid
modification.  The nascent proteins have a N-terminal signal sequence
which differs slightly from the type 1 signal.  The type two signal is
cleaved and an N-terminal cysteine is modified with a lipid.  These
proteins end up anchored in membranes.

Hope this helps - Pugsly has published several good reviews on protein
secretion.